Compact light sensors with symmetrical lighting

ABSTRACT

Provided are methods and systems for concurrent imaging at multiple wavelengths. In one aspect, an imaging device includes at least one objective lens configured to receive light backscattered by an object, a plurality of pixel array photo-sensors, a plurality of bandpass filters covering respective photo-sensors, where each bandpass filter is configured to allow a different respective spectral band to pass through the filter, and a beam steering assembly in optical communication with the at least one objective lens and the photo-sensors. The beam steering assembly directs light received by at least one objective lens from the tissue of a subject to at least one pixel array photo-sensor in the plurality of pixel array photo-sensors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application in is a Continuation-In-Part of U.S. patent applicationSer. No. 14/664,754 entitled “Compact Light Sensor”, filed Mar. 20,2015, which in turn claims priority to U.S. Provisional PatentApplication No. 61/969,039, filed Mar. 21, 2014, and U.S. ProvisionalPatent Application No. 62/090,302, filed Dec. 10, 2014, the disclosuresof which are hereby incorporated by reference herein in their entiretiesfor all purposes.

TECHNICAL FIELD

The present disclosure generally relates to spectroscopy, such ashyperspectral spectroscopy, and in particular, to systems, methods anddevices enabling a compact imaging device.

BACKGROUND

Hyperspectral (also known as “multispectral”) spectroscopy is an imagingtechnique that integrates multiple images of an object resolved atdifferent spectral bands (e.g., ranges of wavelengths) into a singledata structure, referred to as a three-dimensional hyperspectral datacube. Data provided by hyperspectral spectroscopy is often used toidentify a number of individual components of a complex compositionthrough the recognition of spectral signatures of the individualcomponents of a particular hyperspectral data cube.

Hyperspectral spectroscopy has been used in a variety of applications,ranging from geological and agricultural surveying to surveillance andindustrial evaluation. Hyperspectral spectroscopy has also been used inmedical applications to facilitate complex diagnosis and predicttreatment outcomes. For example, medical hyperspectral imaging has beenused to accurately predict viability and survival of tissue deprived ofadequate perfusion, and to differentiate diseased (e.g., cancerous orulcerative) and ischemic tissue from normal tissue.

However, despite the great potential clinical value of hyperspectralimaging, several drawbacks have limited the use of hyperspectral imagingin the clinic setting. In particular, medical hyperspectral instrumentsare costly because of the complex optics and computational requirementsconventionally used to resolve images at a plurality of spectral bandsto generate a suitable hyperspectral data cube. Hyperspectral imaginginstruments can also suffer from poor temporal and spatial resolution,as well as low optical throughput, due to the complex optics and taxingcomputational requirements needed for assembling, processing, andanalyzing data into a hyperspectral data cube suitable for medical use.

Thus, there is an unmet need in the field for less expensive and morerapid means of hyperspectral/multispectral imaging and data analysis.The present disclosure meets these and other needs by providing methodsand systems for concurrently capturing images at multiple wavelengths.

SUMMARY

Various implementations of systems, methods, and devices within thescope of the appended claims each have several aspects, no single one ofwhich is solely responsible for the desirable attributes describedherein. Without limiting the scope of the appended claims, someprominent features are described herein. After considering thisdiscussion, and particularly after reading the section entitled“Detailed Description” one will understand how the features of variousimplementations are used to enable a hyperspectral imaging devicecapable of producing a three-dimensional hyperspectral data cube using aplurality of photo-sensor chips (e.g., CDD, CMOS, etc.) suitable for usein a number for applications, and in particular, for medical use.

One aspect of the present disclosure is directed to an imaging devicecomprising a housing having an exterior and an interior including atleast one objective lens attached to or within the housing. A pluralityof light source sets are radially disposed on the exterior of thehousing about the at least one objective lens. Each light source set inthe plurality of light source sets comprises a first light source thatemits light that is substantially limited to a first spectral range anda second light source that emits light that is substantially limited toa second spectral range. Each light source in each light source set inthe plurality of light source sets is offset from the at least oneobjective lens and positioned so that light from each respective lightsource is backscattered by a tissue of a subject and then passed throughthe at least one objective lens. Each light in each light source set hasa different radial position with respect to the at least one objectivelens. The imaging device further comprises a plurality of pixel arrayphoto-sensors within the housing. The imaging device further comprisesan optical assembly within the interior of the housing. The opticalassembly is in optical communication with the at least one objectivelens. The optical assembly is characterized by further directing lightreceived by at least one objective lens from the tissue of a subject toat least one pixel array photo-sensor in the plurality of pixel arrayphoto-sensors. The imaging device further comprises a plurality ofmulti-bandpass filters (e.g., dual bandpass filters, triple bandpassfilters, quad-bandpass filters). Each respective multi-bandpass filterin the plurality of multi-bandpass filters covers a corresponding pixelarray photo-sensor in the plurality of pixel array photo-sensors therebyselectively allowing a different corresponding spectral band of light,from the light received by the at least one objective lens andredirected by the optical assembly, to pass through to the correspondingpixel array photo-sensor. The imaging device further comprises acontroller. At least one program is non-transiently stored in thecontroller and executable by the controller. The at least one programcauses the controller to perform the method of i) firing a first lightin each light source set in the plurality of light source sets for afirst period of time while not firing the second light source in eachlight source set, ii) collecting a first set of images during the firstperiod of time using at least a first subset of the plurality of pixelarray photo-sensors, iii) firing a second light in each light source setin the plurality of light source sets for a second period of time whilenot firing the first light source in each light source set, and iv)collecting a second set of images during the second period of time usingat least a second subset of the plurality of pixel array photo-sensors.

In a specific embodiment, the multi-bandpass filters are dual bandpassfilters. In some implementations, each respective pixel arrayphoto-sensor in the plurality of pixel array photo-sensors (e.g.,optical detectors 112) is covered by a dual-band pass filter (e.g.,filters 114).

In some implementations, each respective pixel array photo-sensor iscovered by a triple band pass filter, enabling use of a third lightsource and collection of three sets of images at unique spectral bands.For example, four pixel array photo-sensors can collect images at up totwelve unique spectral bands, when each pixel array photo-sensor iscovered by a triple band-pass filter.

In some implementations, each respective pixel array photo-sensor iscovered by a quad-band pass filter, enabling use of a fourth lightsource and collection of four sets of images at unique spectral bands.For example, four pixel array photo-sensors can collect images at up tosixteen unique spectral bands, when each pixel array photo-sensor iscovered by a quad band-pass filter. In yet other implementations, bandpass filters allowing passage of five, six, seven, or more bands eachcan be used to collect larger sets of unique spectral bands.

In some embodiments, each respective dual bandpass filter in theplurality of dual bandpass filters is configured to selectively allowlight corresponding to either of two discrete spectral bands to passthrough to the corresponding photo-sensor. In some embodiments, a firstof the two discrete spectral bands corresponds to a first spectral bandthat is represented in the first spectral range and not in the secondspectral range, and a second of the two discrete spectral bandscorresponds to a second spectral band that is represented in the secondspectral range and not in the first spectral range.

In some embodiments, the optical assembly comprises a plurality of beamsplitters in optical communication with the at least one objective lensand the plurality of pixel array photo-sensors. Each respective beamsplitter in the plurality of beam splitters is configured to split thelight received by the at least one objective lens into at least twooptical paths. A first beam splitter in the plurality of beam splittersis in direct optical communication with the at least one objective lensand a second beam splitter in the plurality of beam splitters is inindirect optical communication with the at least one objective lensthrough the first beam splitter, and the plurality of beam splitterscollectively split light received by the at least one objective lensinto a plurality of optical paths. Each respective optical path in theplurality of optical paths is configured to direct light to acorresponding pixel array photo-sensor in the plurality of pixel arrayphoto-sensors through the respective multi-bandpass filter covering thecorresponding pixel array photo-sensor. In some embodiments, each beamsplitter in the plurality of beam splitters exhibits a ratio of lighttransmission to light reflection of about 50:50. In some embodiments,the beam splitters are wavelength-independent beam splitters. In someembodiments, a first circuit board positioned on a first side of theoptical assembly. A first pixel array photo-sensor and a third pixelarray photo-sensor in the plurality of pixel array photo-sensors arecoupled to the first circuit board, and a second circuit boardpositioned on a second side of the optical assembly opposite to thefirst side. The second circuit board is substantially parallel with thefirst circuit board. A second pixel array photo-sensor and a fourthpixel array photo-sensor in the plurality of pixel array photo-sensorsare coupled to the second circuit board. The first beam splitter isconfigured to split light received from the at least one objective lensinto a first optical path and a second optical path. The first opticalpath is substantially collinear with an optical axis defined by thelight incoming from at least one objectives lens to the beam steeringelement. The second optical path is substantially perpendicular to theoptical axis. The second beam splitter is configured split light fromthe first optical path into a third optical path and a fourth opticalpath. The third optical path is substantially collinear with the firstoptical path, and the fourth optical path is substantially perpendicularto the optical axis. A third beam splitter in the plurality of beamsplitters is configured to split light from the second optical path intoa fifth optical path and a sixth optical path. The fifth optical path issubstantially collinear with the second optical path. The sixth opticalpath is substantially perpendicular to the second optical path, and theoptical path assembly further comprises: a first beam steering elementconfigured to deflect light from the third optical path perpendicular tothe third optical path and onto the first pixel array photo-sensorcoupled to the first circuit board, a second beam steering elementconfigured to deflect light from the fourth optical path perpendicularto the fourth optical path and onto the second pixel array photo-sensorcoupled to the second circuit board, a third beam steering elementconfigured to deflect light from the fifth optical path perpendicular tothe fifth optical path and onto the third pixel array photo-sensorcoupled to the first circuit board, and a fourth beam steering elementconfigured to deflect light from the sixth optical path perpendicular tothe sixth optical path and onto the fourth pixel array photo-sensorcoupled to the second circuit board. In some embodiments, a firstmulti-bandpass filter in the plurality of multi-bandpass filters ispositioned in the third optical path between the first beam splitter andthe first pixel array photo-sensor, a second multi-bandpass filter inthe plurality of multi-bandpass filters is positioned in the fourthoptical path between the second beam splitter and the second pixel arrayphoto-sensor, a third multi-bandpass filter in the plurality ofmulti-bandpass filters is positioned in the fifth optical path betweenthe third beam splitter and the third pixel array photo-sensor, and afourth multi-bandpass filter in the plurality of multi-bandpass filtersis positioned in the sixth optical path between the fourth beam splitterand the fourth pixel array photo-sensor. In some embodiments, theimaging device further comprises a polarizing filter disposed along theoptical axis. In some embodiments, the polarizing filter is adjacent tothe at least one objective lens and before the first beam splitter alongthe optical axis. In some embodiments, the first beam steering elementis a folding prism. In some embodiments, each respective beam splitterand each respective beam steering element is oriented alongsubstantially the same plane. In some embodiments, the first beamsplitter, the second beam splitter, and the third beam splitter eachexhibits a ratio of light transmission to light reflection of about50:50.

In some embodiments, the optical assembly comprises a beam steeringelement that is characterized by a plurality of operating modes, eachrespective operating mode in the plurality of operating modes causingthe beam steering element to be in optical communication with adifferent pixel array photo-sensor in the plurality of pixel arrayphoto-sensors. A first subset of the plurality of operating modes areassociated with firing a first light in each light source set in theplurality of light source set in the first period of time. A secondsubset of the plurality of operating modes are associated with firing asecond light in each light source set in the plurality of light sourceset in the second period of time. In some embodiments, the imagingdevice comprises a plurality of beam steering elements, each respectivebeam steering element configured to direct light in a respective opticalpath to a respective pixel array photo-sensor, of the plurality of pixelarray photo-sensors, corresponding to the respective optical path. Insome embodiments, each one of a first subset of the plurality of beamsteering elements is configured to direct light in a first directionthat is perpendicular to the direction of the light received by theplurality of beam steering elements from the at least one objectivelens, and each one of a second subset of the plurality of beam steeringelements is configured to direct light in a second direction that isperpendicular to the light received by the plurality of beam steeringelements and opposite to the first direction. In some embodiments, thebeam steering element comprises a mirror mounted on an actuator, theactuator having the plurality of operating modes. In some embodiments,the mirror is a single-surface mirror. In some embodiments, the mirroris a two-axis micro electro-mechanical (MEMS) mirror. In someembodiments, the beam steering element comprises an array ofmicromirrors. In some embodiments, the array of micromirrors comprises adigital micromirror device. In some embodiments, the plurality of pixelarray photo-sensors comprises at least four pixel array photo-sensors.In some embodiments, each respective pixel array photo-sensor in theplurality of pixel array photo-sensors is used for detecting a differentfrequency of radiation. In some embodiments, the collecting ii)comprises placing the beam steering element in an operating mode in theplurality of operating modes that causes the beam steering element to bein optical communication with a corresponding pixel array photo-sensorin the plurality of pixel array photo-sensors.

In some embodiments, a housing display is disposed on the exterior ofthe housing, the housing display in electronic communication with thecontroller, and the method further comprises displaying an imagecaptured by a respective pixel array photo-sensor in the plurality ofpixel array photo-sensors on the housing display.

In some embodiments, the plurality of multi-bandpass filters are dualbandpass filters.

In some embodiments, the plurality of light source sets consist of twolight source sets, and a first light source set in the two light sourcesets is arranged with respect to the at least one objective lens so thatthe first light source of the first light source set opposes the firstlight source of the second light source set in the two light sourcesets. The second light source of the first light source set opposes thesecond light source of the second light source set.

In some embodiments, the plurality of light source sets consist of fourlight source sets, and a first light source set in the four light sourcesets is arranged with respect to the at least one objective lens so thatthe first light source of the first light source set opposes the firstlight source of a second light source set in the four light source sets.The second light source of the first light source set opposes the secondlight source of the second light source set.

In some embodiments, the plurality of light source sets consists of 2Nlight source sets, where N is a positive integer. A first light sourceset in the 2N light source sets is arranged with respect to the at leastone objective lens so that the first light source of the first lightsource set opposes the first light source of the second light source setin the 2N light source sets. The second light source of the first lightsource set opposes the second light source of the second light sourceset.

In some embodiments, the plurality of light source sets collectivelycomprises a plurality of first light sources and a plurality of secondlight sources. The first plurality of first light sources are uniformlyradially distributed about the at least one objective lens. Theplurality of second light sources are uniformly radially distributedabout the at least one objective lens. In some embodiments, lightsources in the plurality of first light sources are radially offset fromlight sources in the plurality of second light sources. In someembodiments the plurality of light source sets consists of three lightsource sets. In some embodiments, the plurality of light source setscomprises four or more light source sets.

In some embodiments, the first light source of each light source set inthe plurality of light source sets is a first multi-spectral lightsource covered by a first bandpass filter. The first bandpass filtersubstantially blocks all light emitted by the first light source otherthan the first spectral range. The second light source of each lightsource set in the plurality of light source sets is a secondmulti-spectral light source covered by a second bandpass filter. Thesecond bandpass filter substantially blocks all light emitted by thesecond light source other than the second spectral range. In someembodiments, the first multi-spectral light source is a first whitelight emitting diode and the second multi-spectral light source is asecond white light emitting diode.

In some embodiments, each respective multi-bandpass filter in theplurality of multi-bandpass filters is configured to selectively allowlight corresponding to either of two discrete spectral bands to passthrough to the corresponding pixel array photo-sensor. In someembodiments, a first of the two discrete spectral bands corresponds to afirst spectral band that is represented in the first spectral range andnot in the second spectral range and a second of the two discretespectral bands corresponds to a second spectral band that is representedin the second spectral range and not in the first spectral range.

In some embodiments, the first spectral range is substantiallynon-overlapping with the second spectral range. In some embodiments, thefirst spectral range is substantially contiguous with the secondspectral range.

In some embodiments, the first spectral range comprises 520 nm, 540 nm,560 nm and 640 nm wavelength light and does not include 580 nm, 590 nm,610 nm and 620 nm wavelength light, and the second spectral rangecomprises 580 nm, 590 nm, 610 nm and 620 nm wavelength light and doesnot include 520 nm, 540 nm, 560 nm and 640 nm wavelength light.

In some embodiments, the first set of images includes, for eachrespective pixel array photo-sensor in the plurality of pixel arrayphoto-sensors, an image corresponding to a first spectral bandtransmitted by the corresponding multi-bandpass filter, wherein thelight falling within the first spectral range includes light fallingwithin the first spectral band of each multi-bandpass filter in theplurality of multi-bandpass filters, and the second set of imagesincludes, for each respective pixel array photo-sensor in the pluralityof pixel array photo-sensors, an image corresponding to a secondspectral band transmitted by the corresponding multi-bandpass filter.The light falling within the second spectral range includes lightfalling within the second spectral band of each multi-bandpass filter inthe plurality of multi-bandpass filters. In some embodiments, eachrespective pixel array photo-sensor in the plurality of pixel arrayphoto-sensors is a pixel array that is controlled by a correspondingshutter mechanism that determines an image integration time for therespective pixel array photo-sensor, and a first pixel arrayphoto-sensor in the plurality of pixel array photo-sensors isindependently associated with a first integration time for use duringthe collecting ii) and a second integration time for use during thecollecting iv), where the first integration time is independent of thesecond integration time.

In some embodiments, each image in the plurality of images is amulti-pixel image of the tissue of the subject, and the method furthercombining each image in the plurality of images, on a pixel by pixelbasis, to form a composite image.

In some embodiments, the imaging device is portable and poweredindependent of a power grid during first period of time and the secondperiod of time, the plurality of light source sets collectivelycomprises a plurality of first light sources and a plurality of secondlight sources, the plurality of first light sources collectively provideat least 80 watts of illuminating power during the firing i), theplurality of second light sources collectively provide at least 80 wattsof illuminating power during the firing iii), and the imaging devicefurther comprises a capacitor bank in electrical communication with eachfirst light source and each second light source, wherein a capacitor inthe capacitor bank has a voltage rating of at least 2 volts and acapacitance rating of at least 80 farads.

In some embodiments, two discrete bands of a multi-bandpass filter inthe plurality of multi-bandpass filters are separated by at least 60 nm.

In some embodiments, the imaging device is portable and electricallyindependent of a power grid during the firing i) and the firing iii),and wherein the firing i) occurs for less than 300 milliseconds and thefiring iii) occurs for less than 300 milliseconds.

In some embodiments, the plurality of light source sets collectivelycomprises a plurality of first light sources and a plurality of secondlight sources, and each light source in the plurality of first lightsources is a white light-emitting diode covered by a respective firstlight source filter that blocks light emitted by the whitelight-emitting diode other than the first spectral range. Further, eachlight source in the plurality of second light sources is a whitelight-emitting diode covered by a respective second light source filterthat blocks light emitted by the white light-emitting diode other thanthe second spectral range.

In some embodiments, each light source in each light source set iscovered by a first polarizer, and the at least one objective lens iscovered by a second polarizer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the present disclosure can be understood in greater detail, amore particular description may be had by reference to the features ofvarious implementations, some of which are illustrated in the appendeddrawings. The appended drawings, however, merely illustrate the morepertinent features of the present disclosure and are therefore not to beconsidered limiting, for the description may admit to other effectivefeatures and arrangements.

FIG. 1A is an illustration of a hyperspectral imaging device 100, inaccordance with an implementation.

FIG. 1B is an illustration of a hyperspectral imaging device 100, inaccordance with an implementation.

FIG. 2A and FIG. 2B are illustrations of an optical assembly 102 of ahyperspectral imaging device 100, in accordance with implementations ofthe disclosure.

FIG. 3 is an exploded schematic view of an implementation of an opticalassembly 102 of a hyperspectral imaging device 100.

FIG. 4 is an exploded schematic view of the optical paths 400-404 of animplementation of an optical assembly 102 of a hyperspectral imagingdevice 100.

FIG. 5A, FIG. 5B, and FIG. 5C are two-dimensional schematicillustrations of the optical paths 500-506 and 600-606 ofimplementations of an optical assembly 102 of a hyperspectral imagingdevice 100.

FIG. 6 is an illustration of a front view of implementations of anoptical assembly 102 of a hyperspectral imaging device 100.

FIG. 7 is a partially cut-out illustration of a bottom view of ahyperspectral imaging device 100, in accordance with an implementation.

FIG. 8A is a partially cut-out illustration of a bottom view of ahyperspectral imaging device 100 and optical paths, in accordance withan implementation.

FIG. 8B is a partially cut-out illustration of a bottom view of ahyperspectral imaging device 100 and optical paths, in accordance withanother implementation.

FIG. 9A, FIG. 9B and FIG. 9C are illustrations of framing guides 902projected onto the surface of an object for focusing an image collectedby implementations of a hyperspectral imaging device 100.

FIGS. 9D and 9E are illustrations of point guides 903 projected onto thesurface of an object for focusing an image collected by implementationsof a hyperspectral imaging device 100.

FIG. 10 is a two-dimensional schematic illustration of the optical pathsof an implementation of an optical assembly 102 of a hyperspectralimaging device 100.

FIG. 11 is a two-dimensional schematic illustration of the optical pathsof another implementation of an optical assembly 102 of a hyperspectralimaging device 100.

FIG. 12 is a two-dimensional schematic illustration of the optical pathsof an implementation of an optical assembly 102 of a hyperspectralimaging device 100.

FIG. 13 is an illustration of a first view of another hyperspectralimaging device 100, in accordance with an implementation.

FIG. 14 is an illustration of a second view of the hyperspectral imagingdevice 100 of FIG. 13, in accordance with an implementation.

FIG. 15 is an illustration of a view of another hyperspectral imagingdevice 100, in accordance with an implementation.

FIG. 16 is an illustration of a view of another hyperspectral imagingdevice 100, in accordance with an implementation.

In accordance with common practice the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may not depict all of the componentsof a given system, method or device. Finally, like reference numeralsmay be used to denote like features throughout the specification andfigures.

DETAILED DESCRIPTION

Numerous details are described herein in order to provide a thoroughunderstanding of the example implementations illustrated in theaccompanying drawings. However, the invention may be practiced withoutmany of the specific details. And, well-known methods, components, andcircuits have not been described in exhaustive detail so as not tounnecessarily obscure more pertinent aspects of the implementationsdescribed herein.

Hyperspectral imaging typically relates to the acquisition of aplurality of images, where each image represents a narrow spectral bandcollected over a continuous spectral range. For example, a hyperspectralimaging system may acquire 15 images, where each image represents lightwithin a different spectral band. Acquiring these images typicallyentails taking a sequence of photographs of the desired object, andsubsequently processing the multiple images to generate the desiredhyperspectral image. In order for the images to be useful, however, theymust be substantially similar in composition and orientation. Forexample, the subject of the images must be positioned substantiallyidentically in each frame in order for the images to be combinable intoa useful hyperspectral image. Because images are captured sequentially(e.g., one after another), it can be very difficult to ensure that allof the images are properly aligned. This can be especially difficult inthe medical context, where a clinician is capturing images of a patientwho may move, or who may be positioned in a way that makes imaging thesubject area difficult or cumbersome.

As described herein, a hyperspectral imaging device is described thatconcurrently captures multiple images, where each image is captured in adesired spectral band. Specifically, the disclosed imaging device andassociated methods use multiple photo-sensors to capture a plurality ofimages concurrently. Thus, a user does not need to maintain perfectalignment between the imaging device and a subject while attempting tocapture multiple discrete images, and can instead simply position theimaging device once and capture all of the required images in a singleoperation (e.g., with, one, two, or three exposures) of the imagingdevice. Accordingly, hyperspectral images can be acquired faster andmore simply, and with more accurate results.

Conventional imaging systems also suffer from high power budget demands,requiring the system to be plugged into a power source (e.g., analternating current outlet) for operation. This arises from the use oftunable filter elements, high powered light sources, etc.Advantageously, the optical architecture of the hyperspectral imagingdevices described herein reduces the power burden and overall size ofthe system, allowing production of a truly portable device.

In one implementation, the design of the hyperspectral imaging devicesdescribed herein solve these problems by employing a plurality ofphoto-sensors configured to concurrently acquire images of an object(e.g., a tissue of a patient) at different spectral bands. Eachphoto-sensor is configured to detect a limited number of spectral bands(e.g., 1 or 2 spectral bands), but collectively, the plurality ofphoto-sensors capture images at all of the spectral bands required toconstruct a particular hyperspectral data cube (e.g., a hyperspectraldata cube useful for generating a particular medical diagnosis,performing surveillance, agricultural surveying, industrial evaluation,etc.).

In some implementations, these advantages are realized by separating anddirecting light within an optical assembly in the imaging device suchthat each photo-sensor is irradiated with light of only limited spectralbands. An example of the optical paths created within the opticalassembly of such an implementation is illustrated in FIG. 11, whichsplits light into component spectral bands (e.g., using dichroic beamsplitters and/or beam splitting plates) and direct appropriate spectralbands of light to corresponding photo-sensors. In some alternativeembodiments, these advantageous are realized by separating and directinglight within an optical assembly that is a beam steering device, such asdisclosed in U.S. Pat. No. 9,107,624, which is hereby incorporated byreference.

In some implementations, these advantages are realized by evenlydistributing light towards each photo-sensor within an optical assembly,and then filtering out unwanted wavelengths prior to detection by eachphoto-sensor. An example of the optical paths created within the opticalassembly of such an implementation is illustrated in FIG. 10, which usesoptical elements (e.g., 50:50 beam splitters) to evenly distribute lighttowards filter elements covering each respective photo-sensor.

In yet other implementations, these advantages are realized by employinga hybrid of these two strategies. For example, with an optical assemblythat first separates light (e.g., with a dichroic beam splitter or beamsplitting plate) and then evenly distributes component spectral bands torespective photo-sensors covered by filters having desired passbandspectrums.

In some implementations, one or more of these advantages are realized byemploying a plurality of light source sets radially disposed on theexterior of a housing about at least one objective lens. Each lightsource set in the plurality of light source sets comprises a first lightsource that emits light that is substantially limited to a firstspectral range and a second light source that emits light that issubstantially limited to a second spectral range. Each light source ineach light source set in the plurality of light source sets is offsetfrom the at least one objective lens and positioned so that light fromeach respective light source is backscattered two illumination sourcesin the hyperspectral imaging device. Thus, each first illuminationsource in each light source set is configured to illuminate an objectwith a first sub-set of spectral bands, and each second illuminationsource in each light source set is configured to illuminate the objectwith a second sub-set of spectral bands. The first and second subsets ofspectral bands do not overlap, but together include all the spectralbands required to construct a particular hyperspectral data cube. Theoptical assembly is configured such that two sets of images arecollected, the first while the object is illuminated with each firstlight source in the plurality of light source sets and the second whilethe object is illuminated with each second light source in the pluralityof light source sets. For example, each photo-sensor captures a firstimage at a first spectral band included in the first sub-set of spectralbands and a second image at a second spectral band included in thesecond sub-set of spectral bands.

In some implementations, image capture and processing includes theimaging device collecting a plurality of images of a region of intereston a subject (e.g., a first image captured at a first spectral bandwidthand a second image captured at a second spectral bandwidth). The imagingdevice stores each respective image at a respective memory location(e.g., the first image is stored at a first location in memory and thesecond image is stored at a second location in memory). And the imagingdevice compares, on a pixel-by-pixel basis, e.g., with a processor 210,each pixel of the respective images to produce a hyperspectral image ofthe region of interest of the subject. In some implementations,individual pixel values are binned, averaged, or otherwisearithmetically manipulated prior to pixel-by-pixel analysis, e.g.,pixel-by-pixel comparison includes comparison of binned, averaged, orotherwise arithmetically manipulated pixel values.

Exemplary Implementations

FIG. 1A illustrates a hyperspectral imaging device 100, in accordancewith various implementations. The hyperspectral imaging device 100includes an optical assembly 102 having at least one light source 106for illuminating the surface of an object (e.g., the skin of a subject)and a lens assembly 104 for collecting light reflected and/or backscattered from the object. The optical assembly 102 is mounted onto adocking station 110.

In various implementations, optical assembly 102 is permanently fixedonto the docking station 110 (e.g., optical assembly 102 is held inplace by a substructure of docking station 110 partially encasingoptical assembly 102 and fastened through welding, screws, or othermeans). In other implementations, optical assembly 102 is notpermanently fixed onto the docking station 110 (e.g., optical assembly102 snaps into a substructure of docking station 110).

In various optional implementations, and with reference to FIG. 1A,docking station 110 includes first and second projectors 112-1 and 112-2configured to project light onto the object indicating when thehyperspectral imaging device 100 is positioned at an appropriatedistance from the object to acquire a focused image. This may beparticularly useful where the lens assembly (at least one objectivelens) 104 has a fixed focal distance, such that the image cannot bebrought into focus by manipulation of the lens assembly.

Referring additionally to FIGS. 8A and 9C, in various implementations,first projector 112-1 and second projector 112-2 of FIG. 1A areconfigured to project patterns of light onto the to-be-imaged objectincluding a first portion 902-1 and a second portion 902-2 that togetherform a shape 902 on the object when properly positioned (see, e.g.,FIGS. 8A and 9C). For example, the first portion of the shape 902-1 andthe second portion of the shape 902-1 are configured to converge to formthe shape 902 when the lens 104 is positioned at a predetermineddistance from the object, the predetermined distance corresponding to afocal distance of the lens assembly 104.

In various implementations, first projector 112-1 and second projector112-2 are each configured to project a spot onto the object, such thatthe spots converge when the lens 104 is positioned at a predetermineddistance from the object corresponding to a focus distance of the lens(see, e.g., FIGS. 8B and 9E). Other projections are also contemplated,including other shapes, reticles, images, crosshairs, etc.

Returning to FIG. 1A, in various implementations, docking station 110includes an optical window 114 configured to be positioned between lightsource 106 and an object to be imaged. Window 114 is also configured tobe positioned between lens assembly 104 and the object to be imaged.Optical window 114 protects light source 106 and lens assembly 104, aswell as limits ambient light from reaching lens assembly 104. In variousimplementations, optical window 114 consists of a material that isoptically transparent (or essentially optically transparent) to thewavelengths of light emitted by light source 106. In variousimplementations, optical window 114 consists of a material that ispartially or completely opaque to one or more wavelengths of light notemitted by light source 106. In various implementations, optical window114 serves as a polarizing lens. In various implementations, opticalwindow 114 is open to the external environment (e.g., does not includean installed lens or other optically transparent material).

In various implementations, docking station 110 is configured to receivea mobile device 120, such as a smart phone, a personal digital assistant(PDA), an enterprise digital assistant, a tablet computer, an IPOD, adigital camera, a portable music player, and/or other portableelectronic devices, effectively mounting the mobile device ontohyperspectral imaging device 100. In various implementations, dockingstation 110 is configured to facilitate electronic communication betweenoptical assembly 102 and mobile device 120. In various implementations,mobile device 120 includes display 122 configured to act as a displayfor optical assembly 102 (e.g., as a touch screen display for operatingoptical assembly 102 and/or as a display for hyperspectral imagescollected by optical assembly 102). In various implementations, mobiledevice 120 is configured as a processor for processing one or moreimages collected by optical assembly 102. In various implementations,mobile device 120 is configured to transmit one or more images collectedby optical assembly 102 to an external computing device (e.g., by wiredor wireless communication).

FIG. 1B illustrates another hyperspectral imaging device 100, inaccordance with various implementations, similar to that shown in FIG.1A but including an integrated body 101 (housing) that resembles adigital single-lens reflex (DSLR) camera in that the body has aforward-facing objective lens assembly 104, and a rearward facingdisplay 122. The DSLR-type housing allows a user to easily holdhyperspectral imaging device 100, aim it toward a patient and the regionof interest (e.g., the skin of the patient), and position the device atan appropriate distance from the patient. One will appreciate that theimplementation of FIG. 1B, may incorporate the various featuresdescribed above and below in connection with the device of FIG. 1A.

In various implementations, and similar to the device described above,the hyperspectral imaging device 100 illustrated in FIG. 1B includes aplurality of light source sets 106 radially disposed on the exterior ofthe housing about the objective lens 104. In FIG. 1B, the plurality oflight sets consists of two light sets for a total of four light sources.Each light source set 106 in the plurality of light source setscomprises a first light source (106-1-A, 106-2-A of FIG. 1B) that emitslight that is substantially limited to a first spectral range and asecond light source (106-1-B, 106-2-B of FIG. 1B) that emits light thatis substantially limited to a second spectral range. As illustrated inFIG. 1B, each light source in each light source set in the plurality oflight source sets is offset from the at least one objective lens 104 andpositioned so that light from each respective light source isbackscattered by a tissue of a subject (not shown) and then passedthrough the at least one objective lens 104. As illustrated in FIG. 1B,each light (106-1-A, 106-1-B, 106-2-A, 106-2-A) in each light source sethas a different radial position with respect to the at least oneobjective lens 104. As such, light source sets 106 are for illuminatingthe surface of an object (e.g., the skin of a subject) and the at leastone objective lens 104 is for collecting light reflected and/or backscattered from the object.

In various implementations, and also similar to the device describedabove, the hyperspectral imaging device of FIG. 1B includes first andsecond projectors 112-1 and 112-2 configured to project light onto theobject indicating when the hyperspectral imaging device 100 ispositioned at an appropriate distance from the object to acquire afocused image. As noted above, this may be particularly useful where theat least one objective lens 104 has a fixed focus distance, such thatthe image cannot be brought into focus by manipulation of the lensassembly. As shown in FIG. 1B, the projectors are mounted on a forwardside of body 101.

In various implementations, the body 101 substantially encases andsupports the plurality of light sources 106 and the lens assembly 104 ofthe optical assembly, along with the first and second projectors 112-1and 112-2 and the display 122.

In contrast to the above-described device, various implementations ofthe hyperspectral imaging device of FIG. 1B include photo-sensorsmounted on substantially vertically-oriented circuit boards (see, e.g.,photo sensors 210-1, 210-3). In various implementations, thehyperspectral imaging device includes a live-view camera 103 and aremote thermometer 105. The live-view camera 103 enables the display 122to be used as a viewfinder, in a manner similar to the live previewfunction of DSLRs. The thermometer 105 is configured to measure thetemperature of the patient's tissue surface within the region ofinterest.

FIG. 2A is a cutaway view of the optical assembly 102 for ahyperspectral imaging device 100, in accordance with variousimplementations. The optical assembly 102 may be incorporated into alarger assembly (as discussed herein), or used independently of anyother device or assembly.

As shown in FIG. 2A, the optical assembly 102 includes a casing 202. Asalso shown in an exploded view in FIG. 3, the optical assembly 102 alsoincludes at least one objective lens 104 and provides spacing forindividual light sources (e.g., 106-1-A) in the plurality of sets oflight sources 106, an optical path assembly 204, one or more circuitboards (e.g., circuit board 206 and circuit board 208), and a pluralityof photo-sensors 210 (e.g., photo-sensors 210-1 . . . 210-4). One willappreciate that the imaging device 100 is provided with one or moreprocessors and a memory, referred to herein as a controller. Forexample, such controllers may be integrated or operably coupled with theone or more circuit boards. For instance, in some embodiments, anAT32UC3A364 (ATMEL corporation, San Jose Calif.) microcontroller, orequivalent, coupled to one or more floating point gate arrays, is usedas a controller to collect images from the pixel array photo-sensors.Although illustrated with two circuit boards 206 and 208, in someimplementations, the hyperspectral imaging device has a single circuitboard (e.g., either 206 or 208) and each pixel array photo-sensor 210 iseither mounted on the single circuit board or connected to the circuitboard (e.g., by a flex circuit or wire).

Components of the optical assembly 102 are housed in and/or mounted tothe casing 202. In various implementations, the casing 202 is itselfconfigured to be housed in and/or mounted to another assembly, as shownin FIG. 1A.

The lens assembly 104 (also referred to interchangeably herein as a“lens” or “at least one objective lens”) is an imaging lens that isconfigured to capture light reflected from objects, focus the light, anddirect the light into the optical path assembly 204. In variousimplementations, the lens assembly 104 is a multi-element lens having afixed focal length, a fixed focus distance, and/or is a fixed-focuslens.

The plurality of light source sets 106 are configured to direct lightonto an object to be imaged by the optical assembly 102. Specifically,the plurality of light source sets is configured to illuminate an objectwith light having desired spectral content. Light from the plurality oflight source sets is reflected or backscattered from the object and isthen received by the lens assembly 104 and captured by the plurality ofpixel array photo-sensors in the optical assembly 102.

In various implementations, as discussed herein, the plurality of lightsource sets is configured to operate according to two or more modes ofoperation, where each mode of operation results in the illumination ofthe object with light having different spectral content. For example,referring to FIG. 1A, in a first mode of operation, a first light ineach light source set 106 in the plurality of light source sets is firedfor a first period of time while not firing the second light source ineach light source set. So, in the example of FIG. 1A, light 106-1-A andlight 106-2-A are fired for a first period of time while not firinglight 106-1-B and light 106-2-B. In some embodiments, the first light ineach light source set emits light within a spectral range of 500 nm to600 nm (or any other appropriate spectral range). A first set of imagesis collected during the first period of time using at least a firstsubset of the plurality of pixel array photo-sensors. Next, in a secondmode of operation, the second light in each light set is fired therebyemitting light within a spectral range of 600 nm to 700 nm (or any otherappropriate spectral range) for a second period of time while not firingthe first light source in each light source set. So, in the example ofFIG. 1A, light 106-1-B and light 106-2-B are fired for a second periodof time while not firing light 106-1-A and light 106-2-A. A second setof images is collected during the second period of time using at least asecond subset of the plurality of pixel array photo-sensors.

In various implementations, the each light source in each light sourceset includes a single broadband light source, a plurality of broadbandlight sources, a single narrowband light source, a plurality ofnarrowband light sources, or a combination of one or more broadbandlight source and one or more narrowband light source. Likewise, invarious embodiments, each light source in each light source set includesa plurality of coherent light sources, a single incoherent light source,a plurality of incoherent light sources, or a combination of one or morecoherent and one or more incoherent light sources.

In one implementation, where a light source set is configured to emitlight within two or more spectral ranges, the light source set includestwo or more light sources (e.g., each respective light source includeone or more light emitting devices configured to emit light of the samespectral band), where each respective light source is configured to onlyemit light within one of the two or more spectral ranges. In someembodiments, referring to FIG. 1B, where a light source set isconfigured to emit light within two or more spectral ranges, the lightsource set includes two or more light sources (e.g., light emittingdiodes), where each respective light source is filtered by a respectivefilter (e.g., a bandpass filter). As a specific example, referring toFIG. 1B, light source set 106 comprises light source 106-1-A that isconfigured to emit light within a first spectral range and light source106-1-B that is configured to emit light within a second spectral range.In some embodiments, light source 106-1-A comprises a first set of lightemitting devices that are filtered with a first bandpass filtercorresponding to the first spectral range, and light source 106-1-Bcomprises a second set of light emitting devices filtered with a secondbandpass filters corresponding to the second spectral range. In typicalembodiments the first spectral range is different from, andnon-overlapping, the first second spectral range. In some embodimentsthe first spectral range is different from, but overlapping, the secondspectral range. In some embodiments the first spectral range is the sameas the second spectral range.

In some embodiments, the first light source (e.g., 106-1-A) of a lightsource set 106 consists of a first single light emitting diode (LED) andthe second light source (e.g., 106-1-B) of the light source set consistsof a consists of a second single light emitting diode. An example of asuitable light emitting diode for use as the first single light emittingdiode and the second single light emitting diode in such embodiments isa LUMINUS CBT-140 Whtie LED (Luminus Devices, Inc., Billerica, Mass.).

In some embodiments, the first light source (e.g., 106-1-A) of a lightsource set 106 consists of a first set of light emitting diodes and thesecond light source (e.g., 106-1-B) of the light source set consists ofa second set of light emitting diodes. In some embodiments, the firstset of light emitting devices consists of a first plurality of lightemitting diode and the second set of light emitting devices consists ofa second plurality of light emitting diodes.

In some embodiments each first light source in each light source set 106is not covered by a bandpass filter and natively emits only the firstspectral range. In some embodiments each second light source in eachlight source set 106 is not covered by a bandpass filter and nativelyemits only the second spectral range. In some embodiments, each firstlight source in each light source set 106 emits at least 80 watts ofilluminating power and each second light source in each second lightsource set emits at least 80 watts of illuminating power. In someembodiments, the plurality of light source sets 106 collectivelycomprises a plurality of first light sources and a plurality of secondlight sources, the plurality of first light sources collectively provideat least 80 watts of illuminating power when fired and the plurality ofsecond light sources collectively provide at least 80 watts ofilluminating power when fired. In some embodiments, the plurality offirst light sources collectively provide at least 80 watts, at least 85watts, at least 90 watts, at least 95 watts, at least 100 watts, atleast 105 watts, or at least 110 watts of illuminating power when fired.In some embodiments, the plurality of second light sources collectivelyprovide at least 80 watts, at least 85 watts, at least 90 watts, atleast 95 watts, at least 100 watts, at least 105 watts, or at least 110watts of illuminating power when fired. In some embodiments, thespectral imager 100 is not connected to a main power supply (e.g., anelectrical power grid) during illumination. In other words, in someembodiments, the spectral imager is independently powered, e.g. by abattery, during at least the illumination stages. In some embodiments,in order to achieve the amount of illuminating power needed by theplurality of light source sets 106 (e.g., more than 100 watts ofilluminating power in some embodiments), the light sources are inelectrical communication to the battery through a high performancecapacity bank (not shown). In one such example, the capacitor bankcomprises a board mountable capacitor. In one such example, thecapacitor bank comprises a capacitor having a rating of at least 80farads (F), a peak current of at least 80 amperes (A), and is capable ofdelivering at least 0.7 watt-hours (Whr) of energy during illumination.In one such example, the capacitor bank comprises a capacitor having arating of at least 90 F, a peak current of at least 85 A, and is capableof delivering at least 0.8 Whr of energy during illumination. In onesuch example, the capacitor bank comprises a capacitor having a ratingof at least 95 F, a peak current of at least 90 A, and is capable ofdelivering at least 0.9 Whr of energy during illumination. In one suchexample, the capacitor bank comprises an RSC2R7107SR capacitor (IOXUS,Oneonta, N.Y.), which has a rating of 100 F, a peak current of 95 A, andis capable of delivering 0.1 Whr of energy during illumination.

In one example, the battery used to power the spectral imager, includingthe capacitor bank, has a voltage of at least 6 volts and a capacity ofat least 5000 mAH. In one such example, the battery is manufactured byTENERGY (Fremont, Calif.), is rated for 7.4 V, has a capacitance of 6600mAH, and weighs 10.72 ounces.

In some embodiments, the capacitor bank comprises a single capacitor inelectrical communication with both the light source 106 and the lightsource 107, where the single capacitor has a rating of at least 80 F, apeak current of at least 80 A, and is capable of delivering at least 0.7Whr of energy during illumination. In some embodiments, the capacitorbank comprises a first capacitor in electrical communication with thelight source 106 and a second capacitor in electrical communication withlight source 107, where the first capacitor and the second capacitoreach have a rating of at least 80 F, a peak current of at least 80 A,and are each capable of delivering at least 0.7 Whr of energy duringillumination.

In one implementation, where the plurality of light sources areconfigured to emit light within two or more spectral ranges, in a firstmode of operation, only the first light source in each respective lightsource set is fired (e.g., 106-1-A, 106-2-A, . . . , 106-N-A, where N isa positive integer), and in a second mode of operation, only the secondlight source in each respective light source set is fired (e.g.,106-1-B, 106-2-B, . . . , 106-N-B, wherein N is a positive integer).Here, it will be understood that each first light source in theplurality of light sets is a single first LED and each second lightsource in the plurality of light sources is a single second LED in someembodiments. The same or a similar arrangement of light emitting devicesand bandpass filters may be used in other light sources of the imagingdevice 100. Of course, additional modes of operations (e.g., a thirdmode of operation, a fourth mode of operation, etc.) are also possibleby including additional lights and/or additional bandpass filterscorresponding to additional spectral ranges.

In various implementations, as shown in FIG. 2B, the imaging device hastwo light source sets 106 each consisting of a light source 106-N-A anda light source 106-N-B. As illustrated in FIG. 2B, N=2. In variousembodiments not illustrated in FIG. 2B, the imaging device has one lightsource set, three light source sets, or more than three light sourcesets. In various implementations, each light source set is configured toemit light falling within two substantially non-overlapping spectralranges. For example, in a first mode of operation, a light source106-1-A and a light source 106-2-A emit light within a spectral range of500 nm to 600 nm (or any other appropriate spectral range), and in asecond mode of operation light sources 106-1-B and 106-2-B emit lightwithin a spectral range of 600 nm to 700 nm (or any other appropriatespectral range). In some embodiments as illustrated in FIG. 2B, lightsources 106-1-A and 106-2-A are on opposite sides of the objective lens104 in order to reduce shadowing artifacts on the target object.Further, light sources 106-1-B and 106-2-B are also on opposite sides ofthe objective lens 104 in order to also reduce shadowing artifacts onthe target object.

In some implementations where the hyperspectral imaging device includesa plurality of light source sets where each such light source set hastwo different types of light sources (e.g., light sources 106-N-A and106-N-B, where N is a positive integer), each light source type isconfigured to emit light falling within only one of the twosubstantially non-overlapping spectral ranges. For example, in a firstmode of operation, light sources 106-N-A emit light within a firstspectral range (e.g., 500 nm to 600 nm, or any other appropriatespectral range), and in a second mode of operation, light sources106-N-B emit light within a second spectral range (e.g., 600 nm to 700nm, or any other appropriate spectral range), where N is a positiveinteger.

In some implementations where the hyperspectral imaging device includesa plurality of light source sets and each such light source set has twotypes of light sources (e.g., light sources 106-N-A and 106-N-B, where Nis a positive integer), each light source type is configured to emitlight falling within a corresponding predetermined spectral range. Forexample, in a first mode of operation, light sources 106-N-A emit lightwithin a first spectral range (e.g., one that encompasses 520 nm, 540nm, 560 nm and 640 nm light), and in a second mode of operation, lightsources 106-N-B emit light within a second spectral range (e.g. one thatencompasses 580 nm, 590 nm, 610 nm and 620 nm light), where N is apositive integer.

In some embodiments the first and second modes of light operation applyto light source sets. In other words, while each respective light sourceonly emits light falling within one respective spectral range, eachlight source set collectively operates according to the first and thesecond modes of operation described above.

In various implementations, one or both of the two substantiallynon-overlapping spectral ranges are non-contiguous spectral ranges. Forexample, each first light source of the plurality of light source setsmay emit light having wavelengths between 490 nm and 580 nm in adiscontinuous fashion (e.g., in spectral bands of 490-510 nm and 520-580nm), and each second light source of the plurality of light source setsmay emit light having wavelengths between 575 nm and 640 in a continuousfashion (e.g., in a single spectral band of 575-640 nm). In anotherexample, each first light source of the plurality of light source setsmay emit light having wavelengths between 510 nm and 650 nm in adiscontinuous fashion (e.g., in spectral bands of 510-570 nm and 630-650nm), and each second light source in the plurality of light source setsmay emit light having wavelengths between 570 nm and 630 in a continuousfashion (e.g., in a single spectral band of 570-630 nm). In stillanother example, each first light source in the plurality of lightsource sets may emit light having wavelengths between 515 nm and 645 nmin a discontinuous fashion (e.g., in spectral bands of 515-565 nm and635-645 nm), and each second light source in the plurality of lightsource sets may emit light having wavelengths between 575 nm and 625 ina continuous fashion (e.g., in a single spectral band of 575-625 nm).

In some implementations, each light source in the plurality of lightsource sets is a broadband light source (e.g., white LEDs) with eachfirst light source in the plurality of light sources being covered by adifferent first wavelength filter whereas and each second light sourcein the plurality of light source sets being covered by a secondwavelength filter, where the first and second wavelength filters havesubstantially overlapping pass bands.

In some implementations, each light source in the plurality of lightsource sets is a broadband light source (e.g., white LEDs) and eachfirst light source in the plurality of light source sets is covered by acorresponding first wavelength filter whereas each second light sourcein the plurality of light source sets is covered by a second wavelengthfilter, where the first and second wavelength filters have substantiallynon-overlapping pass bands. The pass bands of filters used in suchimplementations are based on the identity of the spectral bands to beimaged for creation of the hyperspectral data cube.

In one implementation, the spectral bands to be collected are separatedinto two groups. The first group consists of spectral bands withwavelengths below a predetermined wavelength and the second groupconsists of spectral bands with wavelengths above a predeterminedwavelength. For example, if images at eight spectral bands are needed tocreate a particular hyperspectral data cube, the four spectral bandshaving the shortest wavelengths make up the first group and the otherfour spectral bands make up the second group. The first pass band isthen selected such that the first filter allows light having wavelengthscorresponding to the first group, but blocks substantially all lighthaving wavelengths corresponding to the second group. Likewise thesecond pass band is selected such that the second filter allows lighthaving wavelengths corresponding to the second group, but blockssubstantially all light having wavelengths corresponding to the firstgroup.

In another implementation, the spectral bands to be collected areseparated into two groups. The first group consists of a first subset ofspectral bands and the second group consists of a second subset ofspectral bands. In this implementation, the division into the twosubsets is made in such a manner that, upon pairing a spectral band fromthe first subset with a spectral band from the second subset, a minimumpredetermined band separation is guaranteed. For instance, in oneembodiment the first subset comprises 520 nm, 540 nm, 560 nm, and 640 nmwhereas the second subset comprises 580 nm, 590 nm, 510 nm and 620 nmwavelengths. Moreover, four pairs of wavelengths are formed, each paircomprising one band from the first subset and one band from the secondsubset, where the minimum separation between the paired bands is atleast 50 nm. For example, in one embodiment the following pairs areformed: pair (i) 520 nm/590 nm, pair (ii) 540 nm/610 nm, pair (iii) 560nm/620 nm, and pair (iv) 580 nm/640 nm. Advantageously, paired bandswhere the center of each band in the pair is at least 50 nm apart allowsfacilitates the effectiveness of the dual bandpass filters used to coverthe photo-sensors in some embodiments, because the two wavelengthsranges that each such bandpass filter permits to pass through are farenough apart from each other to ensure filter effectiveness.Accordingly, in some implementations, dual pass band filters, allowingpassage of one spectral band from the first group and one spectral bandfrom the second group, are placed in front of each photo-sensor, suchthat one image is captured at a spectral band belonging to the firstgroup (e.g., upon illumination of the object by light source 106), andone image is captured at a spectral band belonging to the second group(e.g., upon illumination of the object by light source 107).

In one implementation, where the hyperspectral data cube is used fordetermining the oxyhemoglobin and deoxyhemoglobin content of a tissue,the first filter has a pass band starting at between 430 nm and 510 nmand ending between 570 nm and 590 nm, and the second filter has a passband starting at between 570 nm and 580 nm and ending between 645 nm and700 nm.

In a first implementation, the imaging device 100 is configured tocollect a set of images, where each image in the set of images iscollected at a discrete spectral band, and the set of images comprisesimages collected at any 4 or more, any 5 or more, any six or more, anyseven or more, or all of the set of discrete spectral bands havingcentral wavelengths {510±5 nm, 530±5 nm, 540±5 nm, 560±5 nm, 580±5 nm,590±5 nm, 620±5 nm, and 660±5 nm}, where each respective spectral bandin the set has a full width at half maximum of less than 15 nm, lessthan 10 nm, or 5 nm or less. In some embodiments of this firstimplementation, a first bandpass filter, covering light source 106, hasa first pass band that permits wavelengths 500±5-550±5 nm and a secondpass band that permits wavelengths 650±5-670±5 nm while all otherwavelengths emitted by the light sources are blocked, and a secondbandpass filter, covering light source 107, has a single pass band thatpermits wavelengths 550±5 nm-630±5 nm while all other wavelengthsemitted by the light sources are blocked. In other such embodiments ofthis first implementation, a first bandpass filter, covering lightsource 106, has a first pass band that permits wavelengths 505±5-545±5nm and a second pass band that permits wavelengths 655±5-665±5 nm whileall other wavelengths emitted by the light sources are blocked, and asecond bandpass filter, covering light source 107, has a single passband that permits wavelengths 555±5 nm-625±5 nm while all otherwavelengths emitted by the light sources are blocked.

In a second implementation, the imaging device 100 is configured tocollect a set of images, where each image in the set of images iscollected at a discrete spectral band, and the set of images comprisesimages collected at any four or more, any five or more, any six or more,any seven or more, or all of the set of discrete spectral bands havingcentral wavelengths {520±5 nm, 540±5 nm, 560±5 nm, 580±5 nm, 590±5 nm,610±5 nm, 620±5 nm, and 640±5 nm} where each respective spectral band inthe set has a full width at half maximum of less than 15 nm, less than10 nm, or 5 nm or less. In some embodiments of this secondimplementation, a first bandpass filter, covering each first lightsource 106-N-A of each light source set, has a first pass band thatpermits wavelengths 510±5-570±5 nm and a second pass band that permitswavelengths 630±5-650±5 nm while all other wavelengths emitted by thelight sources are blocked, and a second bandpass filter, covering eachsecond light source 106-N-B of each light source set, has a single passband that permits wavelengths 570±5 nm-630±5 nm, while all otherwavelengths emitted by the light sources are blocked. In other suchembodiments of this second implementation, a first bandpass filter,covering each first light source 106-N-A of each light set, has a firstpass band that permits wavelengths 515±5-565±5 nm and a second pass bandthat permits wavelengths 635±5-645±5 nm while all other wavelengthsemitted by the light sources are blocked, and a second bandpass filter,covering each second light source 106-N-B of each light source set, hasa single pass band that permits wavelengths 575±5 nm-625±5 nm while allother wavelengths emitted by the light sources are blocked.

In a third implementation, the imaging device 100 is configured tocollect a set of images, where each image in the set of images iscollected at a discrete spectral band, and the set of images comprisesimages collected at any four or more, any five or more, any six or more,any seven or more, or all of the set of discrete spectral bands havingcentral wavelengths {500±5 nm, 530±5 nm, 545±5 nm, 570±5 nm, 585±5 nm,600±5 nm, 615±5 nm, and 640±5 nm}. In such embodiments, each respectivespectral band in the set has a full width at half maximum of less than15 nm, less than 10 nm, or 5 nm or less. In some embodiments of thisthird implementation, a separate first bandpass filter covers each firstlight source 106-N-A of the plurality of light source sets, each suchfirst bandpass filter having a first pass band that permits wavelengths490±5-555±5 nm and a second pass band that permits wavelengths630±5-650±5 nm while all other wavelengths emitted by the light sourcesare blocked. Further, a second bandpass filter covers each second lightsource 106-N-B of each light source set. Each such second bandpassfilter has a single pass band that permits wavelengths 560±5 nm-625±5nm, while all other wavelengths emitted by the light sources areblocked. In other such embodiments of this third implementation, aseparate first bandpass filter covers each first light source 106-N-A ofeach light source set. Each such first bandpass filter has a first passband that permits wavelengths 495±5-550±5 nm and a second pass band thatpermits wavelengths 635±5-645±5 nm while all other wavelengths emittedby the light sources are blocked. Further, a separate second bandpassfilter covers each second light source 106-N-B of each light source set,has a single pass band that permits wavelengths 565±5 nm-620±5 nm whileall other wavelengths emitted by the light sources are blocked.

In some implementations, light sources 106 and 107 are broadband lightsources (e.g., white LEDs). First light source 106 is covered by a shortpass filter (e.g., a filter allowing light having wavelengths below acut-off wavelength to pass through while blocking light havingwavelengths above the cut-off wavelength) and second light source 107 iscovered by a long pass filter (e.g., a filter allowing light havingwavelengths above a cut-on wavelength to pass through while blockinglight having wavelengths below the cut-on wavelength). The cut-off andcut-on wavelengths of the short and long pass filters are determinedbased on the set of spectral bands to be captured by the imaging system.Generally, respective cut-off and cut-on wavelengths are selected suchthat they are longer than the longest wavelength to be captured in afirst set of images and shorter than the shortest wavelength to becaptured in a second set of images (e.g., where the first and second setof images are combined to form a hyperspectral data set).

For example, referring to FIG. 2B and FIG. 3, in one implementation,photo-sensors 210 are each covered by a dual pass band filter 216. Eachdual pass band filter 216 allows light of first and second spectralbands to pass through to the respective photo-sensor 210. Cut-off andcut-on wavelengths for filters covering light sources 106 and 107 areselected such that exactly one pass band from each filter 216 is belowthe cut-off wavelength of the filter covering light source 106 and theother pass band from each filter 216 is above the cut-on wavelength ofthe filter covering light source 107.

In one implementation, where the hyperspectral data cube is used fordetermining the oxyhemoglobin and deoxyhemoglobin content of a tissue,the cut-off wavelength of the short-pass filter covering light source106 and the cut-on wavelength of the long-pass filter covering lightsource 107 are between 565 nm and 585 nm.

In a first implementation, the hyperspectral imaging device isconfigured to collect images at spectral bands having centralwavelengths of 510±5 nm, 530±5 nm, 540±5 nm, 560±5 nm, 580±5 nm, 590±5nm, 620±5 nm, and 660±5 nm, where each respective spectral band has afull width at half maximum of less than 15 nm, and the cut-offwavelength of a short-pass filter covering light source 106 and cut-onwavelength of a long-pass filter covering light source 107 are eachindependently 570±5 nm.

In a second implementation, the hyperspectral imaging device isconfigured to collect images at spectral bands having centralwavelengths of 520±5 nm, 540±5 nm, 560±5 nm, 580±5 nm, 590±5 nm, 610±5nm, 620±5 nm, and 640±5 nm, where each respective spectral band has afull width at half maximum of less than 15 nm, and the cut-offwavelength of a short-pass filter covering light source 106 and cut-onwavelength of a long-pass filter covering light source 107 are eachindependently 585±5 nm.

In a third implementation, the hyperspectral imaging device isconfigured to collect images at spectral bands having centralwavelengths of 500±5 nm, 530±5 nm, 545±5 nm, 570±5 nm, 585±5 nm, 600±5nm, 615±5 nm, and 640±5, where each respective spectral band has a fullwidth at half maximum of less than 15 nm, and the cut-off wavelength ofa short-pass filter covering light source 106 and cut-on wavelength of along-pass filter covering light source 107 are each independently577.5±5 nm.

In various implementations, the imaging device 100 includes three ormore light source types (e.g., 3, 4, 5, 6, or more). In such cases, anyappropriate assignments of spectral ranges (or any other desiredcharacteristic) among the three or more light sources may be used. Forexample, each light source can be configured to emit light according toeach mode of operation desired. Thus, for example, if four substantiallynon-overlapping spectral ranges are required from four light sources,each respective light source may be configured to emit light within eachof the four spectral ranges. In other cases, each respective lightsource may be configured to emit light within a different respective oneof the four spectral ranges. In such instances, it is preferable thatthere be at least two light sources for each such spectral range, witheach such light source being on a different side of the objective lens104 and concurrently fired to prevent shadowing on the tissue ofinterest. In yet other cases, two of the light sources may be configuredto emit light within each of two of the four spectral ranges, and theother two light sources may be configured to emit light within each ofthe remaining two spectral ranges. Other assignments of spectral rangesamong the light sources are also contemplated.

With reference to FIG. 4, the optical assembly 102 also includes anoptical path assembly 204 that directs light received by the lensassembly 104 to a plurality of photo-sensors 210 (e.g., 210-1, . . .210-4) coupled to the first and the second circuit boards 206, 208. Inparticular, as described herein, the optical path assembly 204 includesa plurality of beam splitters 212 (e.g., 212-1 . . . 212-3) and aplurality of beam steering elements 214 (e.g., 214-2, 214-4). The beamsplitters 212 and the beam steering elements 214 are configured to splitthe light received by the lens assembly 104 into a plurality of opticalpaths, and direct those optical paths onto the plurality ofphoto-sensors 210 of the optical assembly 102.

Beam splitters of several different types may be used in the opticalassembly 102 in various implementations. One type of beam splitter thatis used in various implementations is configured to divide a beam oflight into two separate paths that each have substantially the samespectral content. For example, approximately 50% of the light incidenton the beam splitter is transmitted in a first direction, while theremaining approximately 50% is transmitted in a second direction (e.g.,perpendicular to the first direction). Other ratios of the lighttransmitted in the two directions may also be used in variousimplementations. For ease of reference, this type of beam splitter isreferred to herein as a 50:50 beam splitter, and is distinguished from adichroic beam splitter that divides a beam of light into to two separatepaths that each have a different spectral content. For example, adichroic beam splitter that receives light having a spectral range of450-650 nm (or more) may transmit light having a spectral range of450-550 nm in a first direction, and transmit light having a spectralrange of 550-650 nm in a second direction (e.g., perpendicular to thefirst direction).

In addition, other ranges may be utilized, including but not limited todiscontinuous spectral sub-ranges. For example, a first spectral rangeincludes a first spectral sub-range of about 450-550 nm and a secondspectral sub-range of about 615-650 nm, and second, third and fourthspectral ranges may be about 550-615 nm, 585-650 nm and 450-585 nm,respectively. Alternatively, various beam splitters may be utilized tosplit light into a first spectral range having a first spectralsub-range of about 450-530 nm and a second spectral sub-range of about600-650 nm, a second spectral range of about 530-600 nm, a thirdspectral range having at least two discontinuous spectral sub-rangesincluding a third spectral sub-range of about 570-600 nm and a fourthspectral sub-range of about 615-650 nm, a fourth spectral range havingat least two discontinuous spectral sub-ranges including a fifthspectral sub-range of about 450-570 nm and a sixth spectral sub-range ofabout 600-615 nm, at least two discontinuous spectral sub-ranges of afifth spectral range including a seventh spectral sub-range of about585-595 nm and an eighth spectral sub-range of about 615-625 nm, and atleast two discontinuous spectral sub-ranges of a sixth spectral rangeincluding a ninth spectral sub-range of about 515-525 nm and a tenthspectral sub-range of about 555-565 nm.

In various implementations, the beam splitters 212 are 50:50 beamsplitters. In various implementations, the beam splitters 212 aredichroic beam splitters (e.g., beam splitters that divide a beam oflight into separate paths that each have a different spectral content).In various implementations, the beam splitters 212 include a combinationof 50:50 beam splitters and dichroic beam splitters. Several specificexamples of optical assemblies 102 employing beam splitters of varioustypes are discussed herein.

The optical path assembly 204 is configured such that the image that isprovided to each of the photo-sensors (or, more particularly, thefilters that cover the photo-sensors) is substantially identical (e.g.,the same image is provided to each photo-sensor). Because thephoto-sensors 210 can all be operated simultaneously, the opticalassembly 102 is able to capture a plurality of images of the same objectat substantially the same time (thus capturing multiple images thatcorrespond to the same lighting conditions of the object). Moreover,because each photo-sensor 210-n is covered by a bandpass filter 216-nhaving a different passband, each photo-sensor 210-n captures adifferent spectral component of the image. These multiple images, eachrepresenting a different spectral component, are then assembled into ahyperspectral data cube for analysis.

In some embodiments, each photo-sensor 210-n is a pixel array. In someembodiments each photo-sensor 210-n comprises 500,000 pixels, 1,000,000pixels, 1,100,000 pixels, 1,200,000 pixels or more than 1,300,000pixels. In an exemplary embodiment a photo-sensor in the plurality ofphoto-sensors is ½-inch megapixel CMOS digital image sensor such as theMT9M001C12STM monochrome sensor (Aptina Imaging Corporation, San Jose,Calif.).

FIG. 3 is an exploded schematic view that includes the optical assembly102, in accordance with various implementations. FIG. 3 furtherillustrates the arrangement of the various components of the opticalassembly. In particular, the optical assembly 102 includes a firstcircuit board 206 and a second circuit board 208, where the first andsecond circuit boards 206, 208 are substantially parallel to one anotherand are positioned on opposing sides of the optical path assembly 204.In various implementations, the circuit boards 206, 208 are rigidcircuit boards.

Coupled to the first circuit board 206 are a first photo-sensor 210-1and a third photo-sensor 210-3. Coupled to the second circuit board 208are a second photo-sensor 210-2 and a fourth photo-sensor 210-4. Invarious implementations, the photo-sensors 210 are coupled directly totheir respective circuit boards (e.g., they are rigidly mounted to thecircuit board). In various implementations, in order to facilitateprecise alignment of the photo-sensors 210 with respect to the opticalpath assembly 204, the photo-sensors 210 are flexibly coupled to theirrespective circuit board. For example, in some cases, the photo-sensors210 are mounted on a flexible circuit (e.g., including a flexiblesubstrate composed of polyamide, PEEK, polyester, or any otherappropriate material). The flexible circuit is then electronicallycoupled to the circuit board 206, 208. In various implementations, thephoto-sensors 210 are mounted to rigid substrates that are, in turn,coupled to one of the circuit boards 206, 208 via a flexibleinterconnect (e.g., a flexible board, flexible wire array, flexible PCB,flexible flat cable, ribbon cable, etc.).

As noted above, the optical assembly 102 includes a plurality ofbandpass filters 216 (e.g., 216-1 . . . 216-4). The bandpass filters 216are positioned between the photo-sensors 210 and their respectiveoptical outlets of the optical path assembly 204. Thus, the bandpassfilters 216 are configured to filter the light that is ultimatelyincident on the photo-sensors 210. In some embodiments, each bandpassfilter 216 is a dual bandpass filter.

In various implementations, each bandpass filter 216 is configured tohave a different pass band. Accordingly, even though the optical pathassembly 204 provides the same image to each photo-sensor (or, moreparticularly, to the filters that cover the photo-sensors), eachphoto-sensor actually captures a different spectral component of theimage. For example, as discussed in greater detail herein, a firstbandpass filter 216-1 may have a passband centered around 520 nm, and asecond bandpass filter 216-2 may have a passband centered around 540 nm.Thus, when the imaging device 100 captures an exposure, the firstphoto-sensor 210-1 (which is filtered by the first bandpass filter216-1) will capture an image representing the portion of the incominglight having a wavelength centered around 520 nm, and the secondphoto-sensor 210-2 (which is filtered by the second bandpass filter216-2) will capture an image representing the portion of the incominglight having a wavelength around 540 nm. (As used herein, the termexposure refers to a single imaging operation that results in thesimultaneous or substantially simultaneous capture of multiple images onmultiple photo-sensors.) These images, along with the other imagescaptured by the third and fourth photo sensors 210-3, 210-4 (eachcapturing a different spectral band), are then assembled into ahyperspectral data cube for further analysis.

In various implementations, at least a subset of the bandpass filters216 are configured to allow light corresponding to two (or more)discrete spectral bands to pass through the filter. While such filtersmay be referred to herein as dual bandpass filters, this term is meantto encompass bandpass filters that have two discrete passbands as wellas those that have more than two discrete passbands (e.g., triple-bandbandpass filters, quadruple-band bandpass filters, etc.). By usingbandpass filters that have multiple passbands, each photo-sensor can beused to capture images representing several different spectral bands.For example, the hyperspectral imaging device 100 will first illuminatean object with light within a spectral range that corresponds to onlyone of the passbands of each of the bandpass filters, and capture anexposure under the first lighting conditions. Subsequently, thehyperspectral imaging device 100 will illuminate an object with lightwithin a spectral range that corresponds to a different one of thepassbands on each of the bandpass filters, and then capture an exposureunder the second lighting conditions. Thus, because the firstillumination conditions do not include any spectral content that wouldbe transmitted by the second passband, the first exposure results ineach photo-sensor capturing only a single spectral component of theimage. Conversely, because the second illumination conditions do notinclude any spectral content that would be transmitted by the firstpassband, the second exposure results in each photo-sensor capturingonly a single spectral component of the image.

As a more specific example, in various implementations, the bandpassfilters 216-1 through 216-4 each include one passband falling within therange of 500-585 nm, and a second passband falling within the range of585-650 nm, as shown below in table (1):

TABLE 1 Exemplary Central Wavelengths of Pass- bands for Filters216-1-216-4 Filter 216-1 Filter 216-2 Filter 216-3 Filter 216-4 Passband1 520 nm 540 nm 560 nm 580 nm Passband 2 590 nm 610 nm 620 nm 640 nm

In one implementation, the plurality of light source sets 106 have twomodes of operation: in a first mode of operation, a first light sourcein each light source set 106 emits light having wavelengths according toa first set of spectral bands (e.g., below 585 nm, such as between 500nm and 585 nm); in a second mode of operation, a second light source ineach light source set emits light having wavelengths according to asecond set of spectral bands (e.g., above 585 nm, such as between 585 nmand 650 nm). Thus, when the first exposure is captured using the firstillumination mode, four images are captured, where each imagecorresponds to a single spectral component of the incoming light.Specifically, the image captured by the first sensor 210-1 will includesubstantially only that portion of the incoming light falling within afirst passband (e.g., centered around 520 nm), the image captured by thesecond sensor 210-2 will include substantially only that portion of theincoming light falling within a second passband (e.g., centered around540 nm), and so on. When the second exposure is captured using thesecond illumination mode, four additional images are captured, whereeach image corresponds to a single spectral component of the incominglight. Specifically, the image captured by the first sensor 210-1 willinclude substantially only that portion of the incoming light fallingwithin the other pass band allowed by the dual band filter 216-1 (e.g.,centered around 590 nm), the image captured by the second sensor 210-2will include substantially only that portion of the incoming lightfalling within the other pass band allowed by dual band filter 216-2(e.g., centered around 610 nm), and so on. The eight images resultingfrom the two exposures described above are then assembled into ahyperspectral data cube for further analysis.

In another implementation, as illustrated in FIG. 2B, the hyperspectralimaging device has two light source sets, and each light source in eachlight source set is configured to illuminate an object with a differentset of spectral bands. The hyperspectral imaging device has two modes ofoperation: in a first mode of operation, light sources 106-1-A and102-2-A emit light having wavelengths according to a first set ofspectral bands. In a second mode of operation, light sources 106-1-B and106-2-B emit light having wavelengths according to a second set ofspectral bands. Thus, when the first exposure is captured using thefirst illumination mode, four images are captured, where each imagecorresponds to a single spectral component of the incoming light.Specifically, the image captured by the first sensor 210-1 during thefirst mode of operation will include substantially only that portion ofthe incoming light falling within a first passband (e.g., centeredaround 520 nm), the image captured by the second sensor 210-2 during thefirst mode of operation will include substantially only that portion ofthe incoming light falling within a second passband (e.g., centeredaround 540 nm), and so on. When the second exposure is captured usingthe second illumination mode, four additional images are captured, whereeach image corresponds to a single spectral component of the incominglight. Specifically, the image captured by the first sensor 210-1 willinclude substantially only that portion of the incoming light fallingwithin the other pass band allowed by the dual band filter 216-1 (e.g.,centered around 590 nm), the image captured by the second sensor 210-2will include substantially only that portion of the incoming lightfalling within the other pass band allowed by dual band filter 216-2(e.g., centered around 610 nm), and so on. The eight images resultingfrom the two exposures described above are then assembled into ahyperspectral data cube for further analysis. In typical embodiments,each such image is a multi-pixel image. In some embodiments, thisassembly involves combining each image in the plurality of images, on apixel by pixel basis, to form a composite image.

In the above examples, each filter 216-n has two passbands. However, invarious implementations, the filters do not all have the same number ofpassbands. For example, if fewer spectral bands need to be captured, oneor more of the filters 216-n may have only one passband. Similarly, oneor more of the filters 216-n may have additional passbands. In thelatter case, the light source 104 will have additional modes ofoperation, where each mode of operation illuminates an object with lightthat falls within only 1 (or none) of the passbands of each sensor.

FIG. 4 is an exploded schematic view of a portion of the opticalassembly 102, in accordance with various implementations, in which theoptical paths formed by the optical path assembly 204 are shown. Theoptical path assembly 204 channels light received by the lens assembly104 to the various photo-sensors 210 of the optical assembly 102.

Turning to FIG. 4, the optical assembly 102 includes a first beamsplitter 212-1, a second beam splitter 212-2, and a third beam splitter212-3. Each beam splitter is configured to split the light received bythe beam splitter into at least two optical paths. For example, beamsplitters for use in the optical path assembly 204 may split an incomingbeam into one output beam that is collinear to the input beam, andanother output beam that is perpendicular to the input beam.

Specifically, the first beam splitter 212-1 is in direct opticalcommunication with the lens assembly 104, and as shown in FIG. 10,splits the incoming light (represented by arrow 400) into a firstoptical path 401 and a second optical path 402. The first optical path401 is substantially collinear with the light entering the first beamsplitter 212-1, and passes to the second beam splitter 212-2. The secondoptical path 402 is substantially perpendicular to the light enteringthe first beam splitter 212-1, and passes to the third beam splitter212-3. In various implementations, the first beam splitter 212-1 is a50:50 beam splitter. In other implementations, the first beam splitter212-1 is a dichroic beam splitter.

With continued reference to FIG. 10, the second beam splitter 212-2 isadjacent to the first beam splitter 212-1 (and is in direct opticalcommunication with the first beam splitter 212-1), and splits theincoming light from the first beam splitter 212-1 into a third opticalpath 403 and a fourth optical path 404. The third optical path 403 issubstantially collinear with the light entering the second beam splitter212-2, and passes through to the first beam steering element 214-1 (seeFIG. 4). The fourth optical path is substantially perpendicular to thelight entering the second beam splitter 212-2, and passes through to thesecond beam steering element 214-2. In various implementations, thesecond beam splitter 212-2 is a 50:50 beam splitter. In otherimplementations, the second beam splitter 212-2 is a dichroic beamsplitter.

The beam steering elements 214 (e.g., 214-1 . . . 214-4 shown in FIG. 4)are configured to change the direction of the light that enters one faceof the beam steering element. Beam steering elements 214 are anyappropriate optical device that changes the direction of light. Forexample, in various implementations, the beam steering elements 214 areprisms (e.g., folding prisms, bending prisms, etc.). In variousimplementations, the beam steering elements 214 are mirrors. In variousimplementations, the beam steering elements 214 are other appropriateoptical devices or combinations of devices.

Returning to FIG. 4, the first beam steering element 214-1 is adjacentto and in direct optical communication with the second beam splitter212-2, and receives light from the third optical path (e.g., the outputof the second beam splitter 212-2 that is collinear with the input tothe second beam splitter 212-2). The first beam steering element 214-1deflects the light in a direction that is substantially perpendicular tothe fourth optical path (and, in various implementations, perpendicularto a plane defined by the optical paths of the beam splitters 212, e.g.,the x-y plane) and onto the first photo-sensor 210-1 coupled to thefirst circuit board 206 (FIG. 3). The output of the first beam steeringelement 214-1 is represented by arrow 411 (see FIG. 4).

The second beam steering element 214-2 is adjacent to and in directoptical communication with the second beam splitter 212-2, and receiveslight from the fourth optical path (e.g., the perpendicular output ofthe second beam splitter 212-2). The second beam steering element 214-2deflects the light in a direction that is substantially perpendicular tothe third optical path (and, in various implementations, perpendicularto a plane defined by the optical paths of the beam splitters 212, e.g.,the x-y plane) and onto the second photo-sensor 210-2 coupled to thesecond circuit board 208 (FIG. 3). The output of the second beamsteering element 214-2 is represented by arrow 412 (see FIG. 4).

As noted above, the first beam splitter 212-1 passes light to the secondbeam splitter 212-2 along a first optical path (as discussed above), andto the third beam splitter 212-3 along a second optical path.

With reference to FIG. 10, the third beam splitter 212-3 is adjacent tothe first beam splitter 212-1 (and is in direct optical communicationwith the first beam splitter 212-1), and splits the incoming light fromthe first beam splitter 212-1 into a fifth optical path 405 and a sixthoptical path 406. The fifth optical path 405 is substantially collinearwith the light entering the third beam splitter 212-3, and passesthrough to the third beam steering element 214-3 (see FIG. 4). The sixthoptical path is substantially perpendicular to the light entering thethird beam splitter 212-3, and passes through to the fourth beamsteering element 214-4. In various implementations, the third beamsplitter 212-3 is a 50:50 beam splitter. In other implementations, thethird beam splitter 212-3 is a dichroic beam splitter.

The third beam steering element 214-3 (see FIG. 4) is adjacent to and indirect optical communication with the third beam splitter 212-3, andreceives light from the fifth optical path (e.g., the output of thethird beam splitter 212-3 that is collinear with the input to the thirdbeam splitter 212-3). The third beam steering element 214-3 deflects thelight in a direction that is substantially perpendicular to the thirdoptical path (and, in various implementations, perpendicular to a planedefined by the optical paths of the beam splitters 212, e.g., the x-yplane) and onto the third photo-sensor 210-3 coupled to the firstcircuit board 206 (FIG. 3). The output of the third beam steeringelement 214-3 is represented by arrow 413 (see FIG. 4).

The fourth beam steering element 214-4 is adjacent to and in directoptical communication with the third beam splitter 212-3, and receiveslight from the sixth optical path (e.g., the perpendicular output of thethird beam splitter 212-3). The fourth beam steering element 214-4deflects the light in a direction that is substantially perpendicular tothe sixth optical path (and, in various implementations, perpendicularto a plane defined by the optical paths of the beam splitters 212, e.g.,the x-y plane) and onto the fourth photo-sensor 210-4 coupled to thesecond circuit board 208 (FIG. 3). The output of the fourth beamsteering element 214-4 is represented by arrow 414 (see FIG. 4).

As shown in FIG. 4, the output paths of the first and third beamsteering elements 214-1, 214-3 are in opposite directions than theoutput paths of the second and fourth beam steering elements 214-2,214-4. Thus, the image captured by the lens assembly 104 is projectedonto the photo-sensors mounted on the opposite sides of the imageassembly 102. However, the beam steering elements 212 need not facethese particular directions. Rather, any of the beam steering elements212 can be positioned to direct the output path of each beam steeringelement 212 in any appropriate direction. For example, in variousimplementations, all of the beam steering elements 212 direct light inthe same direction. In such cases, all of the photo-sensors may bemounted on a single circuit board (e.g., the first circuit board 206 orthe second circuit board 208, FIG. 3). Alternatively, in variousimplementations, one or more of the beam steering elements 212 directslight substantially perpendicular to the incoming light, but insubstantially the same plane defined by the optical paths of the beamsplitters 212 (e.g., within the x-y plane). In yet otherimplementations, one or more beam steering elements 214 are excludedfrom the imaging device, and the corresponding photo-sensors 210 arepositioned orthogonal to the plane defined by optical paths 400-1 .to400-6.

FIG. 5A is a cross-sectional view of the optical assembly 102 and theoptical path assembly 204 in accordance with various implementations,and FIG. 10 is a two-dimensional schematic illustration of the opticalpaths within the optical path assembly 204. Although illustrated with asingle light source 106, this optical path assembly is typicallyimplemented using a plurality of light source sets, one of which isillustrated in FIG. 5C and two of which are illustrated in FIGS. 3 and4. Light from the lens assembly 104 enters the first beam splitter210-1, as indicated by arrow 400. The first beam splitter 210-1 splitsthe incoming light (arrow 400) into a first optical path (arrow 401)that is collinear to the incoming light (arrow 400). Light along thefirst optical path (arrow 401) is passed through to the second beamsplitter 210-2. The first beam splitter 210-1 also splits the incominglight (arrow 400) into a second optical path (arrow 402) that isperpendicular to the incoming light (arrow 400). Light along the secondoptical path (arrow 402) is passed through to the third beam splitter210-3.

Light entering the second beam splitter 210-2 (arrow 402) is furthersplit into a third optical path (arrow 403) that is collinear with theincoming light (arrow 400 and/or arrow 402). Light along the thirdoptical path (arrow 403) is passed to the first beam steering element214-1 (see, e.g., FIG. 4), which steers the light onto the firstphoto-sensor 210-1. As discussed above, in various implementations, thefirst beam steering element 214-1 deflects the light in a direction thatis perpendicular to the light entering the second beam splitter and outof the plane defined by the beam splitters (e.g., in a positivez-direction, or out of the page, as shown in FIG. 5).

Light entering the second beam splitter 210-2 (arrow 402) is furthersplit into a fourth optical path (arrow 404) that is perpendicular tothe incoming light (arrow 400 and/or arrow 402). Light along the fourthoptical path (arrow 404) is passed to the second beam steering element214-2, which steers the light onto the second photo-sensor 210-2. Asdiscussed above, in various implementations, the second beam steeringelement 214-2 deflects the light in a direction that is perpendicular tothe light entering the second beam splitter and out of the plane definedby the beam splitters (e.g., in a negative z-direction, or into thepage, as shown in FIG. 5).

Light entering the third beam splitter 210-3 (arrow 402) is furthersplit into a fifth optical path (arrow 405) that is collinear with thelight incoming into the third beam splitter 210-3 (arrow 402). Lightalong the fifth optical path (arrow 405) is passed to the third beamsteering element 214-3 (see, e.g., FIG. 4), which steers the light ontothe third photo-sensor 210-3. As discussed above, in variousimplementations, the third beam steering element 214-3 deflects thelight in a direction that is perpendicular to the light entering thethird beam splitter and out of the plane defined by the beam splitters(e.g., in a positive z-direction, or out of the page, as shown in FIG.5).

Light entering the third beam splitter 210-3 (arrow 402) is furthersplit into a sixth optical path (arrow 406) that is perpendicular to thelight incoming into the third beam splitter 210-3 (arrow 402). Lightalong the sixth optical path (arrow 406) is passed to the fourth beamsteering element 214-4, which steers the light onto the fourthphoto-sensor 210-4. As discussed above, in various implementations, thefourth beam steering element 214-4 deflects the light in a directionthat is perpendicular to the light entering the third beam splitter andout of the plane defined by the beam splitters (e.g., in a negativez-direction, or into the page, as shown in FIG. 5).

FIG. 5B is a top schematic view of the optical assembly 102 and theoptical path assembly 204 in accordance with various implementations,and FIG. 12 is a two-dimensional schematic illustration of the opticalpaths within the optical path assembly 204. Although illustrated with asingle light source set, the optical path is more typically illuminatedby a plurality of sets of light sources as illustrated in FIGS. 3 and 4,where each light source in the light source set is configured to operatein one or more operating modes (e.g., two operating modes as describedherein).

Light from the lens assembly 104 enters the first beam splitter 220-1,as indicated by arrow 600. The first beam splitter 220-1 splits theincoming light (arrow 600) into a first optical path (arrow 601) that isperpendicular to the incoming light (arrow 600) and a second opticalpath (arrow 602) that is collinear to the incoming light (arrow 600).Light along the first optical path (arrow 601) is passed to a beamsteering element in similar manner described above, which steers thelight onto the third photo-sensor 210-3. As discussed above, in variousimplementations, the steering element deflects the light in a directionthat is perpendicular to the first optical path (arrow 601) and out ofthe plane (e.g., in a positive z-direction, or out of the page) towardthe third photo-sensor 210-3. Light along the second optical path (arrow602) is passed through to a second beam splitter 220-2.

The second beam splitter 220-2 splits the incoming light (arrow 602)into a third optical path (arrow 603) that is perpendicular to theincoming light (arrow 602) and a fourth optical path (arrow 604) that iscollinear to the incoming light (arrow 602). Light along the thirdoptical path (arrow 603) is passed to another beam steering element insimilar manner described above, which steers the light onto the secondphoto-sensor 210-2. As discussed above, in various implementations, thesteering element deflects the light in a direction that is perpendicularto the third optical path (arrow 603) and out of the plane (e.g., in anegative z-direction, or into the page) toward the second photo-sensor210-2. Light along the fourth optical path (arrow 604) is passed throughto a third beam splitter 220-3.

The third beam splitter 220-3 splits the incoming light (arrow 604) intoa fifth optical path (arrow 605) that is perpendicular to the incominglight (arrow 604) and a sixth optical path (arrow 606) that is collinearto the incoming light (arrow 604). Light along the fifth optical path(arrow 605) is passed to another beam steering element, which steers thelight onto the fourth photo-sensor 210-4. As discussed above, in variousimplementations, the steering element deflects the light in a directionthat is perpendicular to the firth optical path (arrow 605) and out ofthe plane (e.g., in a negative z-direction, or into the page) toward thefourth photo-sensor 210-4. Light along the sixth optical path (arrow606) is passed to another beam steering element, which steers the lightonto the first photo-sensor 210-1. As discussed above, in variousimplementations, the steering element deflects the light in a directionthat is perpendicular to the sixth optical path (arrow 606) and out ofthe plane (e.g., in a positive z-direction, or out of the page) towardthe first photo-sensor 210-1.

FIG. 6 is a front schematic view of the optical assembly 102, inaccordance with various implementations. For clarity, the lens assembly104 and the light source sets 106 are not shown. The lines within thebeam splitters 212 and the beam steering elements 214 further depict thelight paths described herein. For example, the line designated by arrow404 illustrates how the beam steering element 214-2 deflects the lightreceived from the beam splitter 212-2 onto the photo-sensor 210-2.Further, the line designated by arrow 402 illustrates how the beamsteering element 214-3 deflects the light received from the beamsplitter 212-3 onto the photo-sensor 210-3. Arrows 411-414(corresponding to the optical paths indicated in FIG. 4) furtherillustrate how the beam steering elements 214 direct light to theirrespective photo-sensors 210.

In the instant application, the geometric terms such as parallel,perpendicular, orthogonal, coplanar, collinear, etc., are understood toencompass orientations and/or arrangements that substantially satisfythese geometric relationships. For example, when a beam steering elementdeflects light perpendicularly, it is understood that the beam steeringelement may deflect the light substantially perpendicularly. As a morespecific example, in some cases, light may be determined to beperpendicular (or substantially perpendicular) when the light isdeflected 90+/−1 degrees from its input path. Other deviations fromexact geometric relationships are also contemplated.

As noted above, the optical assembly 102 can use various combinations of50:50 beam splitters and dichroic beam splitters. In a first example,the first beam splitter 212-1, the second beam splitter 212-2, and thethird beam splitter 212-3 are all 50:50 beam splitters. An exampleoptical assembly 102 with this selection of beam splitters isillustrated in FIG. 10.

In a second example, the first beam splitter 212-1 is a dichroic beamsplitter, and the second beam splitter 212-2 and the third beam splitter212-3 are both 50:50 beam splitters. An example optical assembly 102with this selection of beam splitters is illustrated in FIG. 11.

In a third example, the first beam splitter 212-1, the second beamsplitter 212-2, and the third beam splitter 212-3 are all dichroic beamsplitters. An example optical assembly 102 with this selection of beamsplitters is illustrated in FIG. 12.

FIG. 7 is a cutaway view of an implementation of imaging device 100,illustrating light paths 410 and 411, corresponding to light emittedfrom light source 106 and illuminating the object being imaged, as wellas light path 400, corresponding to light backscattered from the object.

The use of polarized illumination is advantageous because it eliminatessurface reflection from the skin and helps to eliminate stray lightreflection from off axis imaging directions. Accordingly, in variousimplementations, polarized light is used to illuminate the object beingimaged. In various implementations, the light is polarized with respectto a coordinate system relating to the plane of incidence formed by thepropagation direction of the light (e.g., the light emitted by lightsource 106) and a vector perpendicular to the plane of the reflectingsurface (e.g., the object being imaged). The component of the electricfield parallel to the plane of incidence is referred to as thep-component and the component perpendicular to the plane is referred toas the s-component. Accordingly, polarized light having an electricfield along the plane of incidence is “p-polarized,” while polarizedlight having an electric field normal to the plane is “s-polarized.”

Light can be polarized by placing a polarization filter in the path ofthe light. The polarizer allows light having the same polarization(e.g., p-polarized or s-polarized) to pass through, while reflectinglight having the opposite polarization. Because the polarizer ispassively filtering the incident beam, 50% of non-polarized light islost due to reflection off the polarizing filter. In practice,therefore, a non-polarized light source must produce twice the desiredamount of polarized illuminating light, at twice the power consumption,to account for this loss. Advantageously, in various implementations,the imaging device recaptures and reverses the polarity light reflectedoff the polarization filter, using a polarization rotator (e.g., apolarization rotation mirror). In various implementations, at least 95%of all of the light received by the polarizer from the at least onelight source may be illuminated onto the object.

Returning to FIG. 7, in one implementation, light emitted from lightsource 106 along optical path 410 is received by polarizer 700. Theportion of the light having the same polarization as polarizer 700(e.g., s- or p-polarization) passes through polarizer 700 and isdirected, through optical window 114, onto the surface of the object.The portion of the light having the opposite polarization as polarizer700 is reflected orthogonally along optical path 411, directed topolarization rotator 702. Polarization rotator 700 reverses thepolarization of the light (e.g., reverses the polarization to match thepolarization transmitted through polarizer 700) and reflects the light,through optical window 114, onto the surface of the object. Polarizedlight backscattered from the object, returning along optical path 400,is captured by lens assembly 104 and is directed internal to opticalassembly 102 as described above.

In this fashion, accounting for incidental loss of light along theoptical path, substantially all the light emitted from a light source106 is projected onto the surface of the object being imaged in apolarized manner. This eliminates the need for light source 106 toproduce twice the desired amount illuminating light, effectivelyreducing the power consumption from illumination by 50%.

FIGS. 9A-9C are illustrations of framing guides projected onto thesurface of an object for focusing an image collected by animplementation of an imaging device 100.

As noted above, in various implementations, the lens assembly 104 has afixed focal distance. Thus, images captured by the imaging device 100will only be in focus if the imaging device 110 is maintained at anappropriate distance from the object to be imaged. In variousimplementations, the lens assembly 104 has a depth of field of a certainrange, such that objects falling within that range will be suitablyfocused. For example, in various implementations, the focus distance ofthe lens assembly 104 is 24 inches, and the depth of field is 3 inches.Thus, objects falling anywhere from 21 to 27 inches away from the lensassembly 104 will be suitably focused. These values are merelyexemplary, and other focus distances and depths of field are alsocontemplated.

Referring to FIG. 8A-8B, to facilitate accurate positioning of theimaging device 100 with respect to the object to be imaged, the dockingstation 110 includes first and second projectors 112 (e.g., 112-1,112-2) configured to project light (e.g., light 901, 903 in FIGS. 8A and8B, respectively) onto the object indicating when the imaging device 100is positioned at an appropriate distance from the object to acquire afocused image. In various implementations, with reference to FIGS.9A-9C, the first projector 112-1 and the second projector 112-2 areconfigured to project a first portion 902-1 and a second portion 902-2of a shape 902 onto the object (FIGS. 9A-9C), respectively. The firstportion of the shape 902-1 and the second portion of the shape 902-1 areconfigured to converge to form the shape 902 when the lens 104 ispositioned at a predetermined distance from the object, thepredetermined distance corresponding to a focus distance of the lens.

In one implementation, the framing guides converge to form a closedrectangle on the surface of the object when the lens of the imagingdevice 100 is positioned at predetermined distance from the objectcorresponding to the focus distance of the lens (FIG. 9C). When the lensof the imaging device 100 is positioned at distance from the object thatis less than the predetermined distance, the framing guides remainseparated (FIG. 9A). When the lens of the imaging device 100 ispositioned at distance from the object that is greater than thepredetermined distance, the framing guides cross each other (FIG. 9B).

In various implementations, the framing guides represent all orsubstantially all the area of the object that will be captured by theimaging device 100. In various implementations, at least all of theobject that falls inside the framing guides will be captured by theimaging device 100.

In various implementations, as illustrated in FIG. 8B, first projector112-1 and second projector 112-2 are each configured to project a spotonto the object (e.g., spots 904-1 and 904-2, illustrated in FIG. 9D),such that the spots converge (e.g., at spot 904 in FIG. 9E) when thelens 104 is positioned at a predetermined distance from the object, thepredetermined distance corresponding to a focus distance of the lens.When the lens of the imaging device 100 is positioned at distance fromthe object that is less than or greater than the predetermined distance,the projected spots diverge from each other (FIG. 9D).

FIG. 1B illustrates another imaging device 100, in accordance withvarious implementations, similar to that shown in FIG. 1A but includingan integrated body 101 that resembles a digital single-lens reflex(DSLR) camera in that the body has a forward-facing lens assembly 104,and a rearward facing display 122. The DSLR-type housing allows a userto easily hold imaging device 100, aim it toward a patient and theregion of interest (e.g., the skin of the patient), and position thedevice at an appropriate distance from the patient. One will appreciatethat the implementation of FIG. 1B, may incorporate the various featuresdescribed above and below in connection with the device of FIG. 1A.

In various implementations, and similar to the device described above,the imaging device 100 illustrated in FIG. 1B includes an opticalassembly having a plurality of light source sets 106 for illuminatingthe surface of an object (e.g., the skin of a subject) and a lensassembly 104 for collecting light reflected and/or back scattered fromthe object.

In various implementations, and also similar to the device describedabove, the imaging device of FIG. 1B includes first and secondprojectors 112-1 and 112-2 configured to project light onto the objectindicating when the imaging device 100 is positioned at an appropriatedistance from the object to acquire a focused image. As noted above,this may be particularly useful where the lens assembly 104 has a fixedfocal distance, such that the image cannot be brought into focus bymanipulation of the lens assembly. As shown in FIG. 1B, the projectorsare mounted on a forward side of body 101.

In various implementations, the body 101 substantially encases andsupports the light source sets 106 and the lens assembly 104 of theoptical assembly, along with the first and second projectors 112-1 and112-2 and the display 122.

FIGS. 13 and 14 collectively illustrate another configuration forimaging device 100, in accordance with various implementations, similarto that shown in FIG. 1B but including more detail regarding anembodiment of integrated body 101 and forward-facing lens assembly 104,and a rearward facing display 122. The housing 101 allows a user toeasily hold imaging device 100, aim it toward a patient and the regionof interest (e.g., the skin of the patient), and position the device atan appropriate distance from the patient. One will appreciate that theimplementation of FIGS. 13 and 14 may incorporate the various featuresdescribed herein in connection with the device of FIGS. 1A and 1B.

In various implementations, and similar to the device described above,the imaging device 100 illustrated in FIGS. 13 and 14 includes anoptical assembly and a plurality of light source sets 106 forilluminating the surface of an object (e.g., the skin of a subject) anda lens assembly 104 for collecting light reflected and/or back scatteredfrom the object.

In various implementations, and also similar to the device described inFIGS. 1A and 1B, the imaging device of FIG. 13 includes first and secondprojectors 112-1 and 112-2 configured to project light onto the objectindicating when the imaging device 100 is positioned at an appropriatedistance from the object to acquire a focused image. As noted above,this may be particularly useful where the lens assembly 104 has a fixedfocus distance, such that the image cannot be brought into focus bymanipulation of the lens assembly. As shown in FIG. 13, the projectorsare mounted on a forward side of body 101.

In various implementations, the body 101 substantially encases andsupports the light sets 106 and the lens assembly 104 of the opticalassembly, along with the first and second projectors 112-1 and 112-2. Invarious implementations, the imaging device 101 of FIG. 13 includes alive-view camera 103 and a remote thermometer 105.

FIG. 13 illustrates an embodiment in which the imaging device consist oftwo light source sets and the first light source set 106-1 in the twolight source sets is arranged with respect to the at least one objectivelens 104 so that the first light source 106-1-A of the first lightsource set opposes the first light source 106-2-A of the second lightsource set in the two light source sets, and the second light source106-1-B of the first light source set opposes the second light source106-2-B of the second light source set (across the objective lens).

FIG. 15 illustrates an embodiment in which the imaging device consist offour light source sets (106-1, 106-2, 106-3, and 104-5), and a firstlight source set 106-1 in the four light source sets is arranged withrespect to the at least one objective lens 104 so that the first lightsource 106-1-A of the first light source set opposes the first lightsource 106-3-A of a second light source set 106-3 in the four lightsource sets, and the second light source 106-1-B of the first lightsource set opposes the second light source 106-3-B of the second lightsource set 103.

FIG. 16 illustrates an embodiment in which the imaging device comprisestwo light source sets 106-1 and 106-2 and a first light source set 106-1in the two light source sets is arranged with respect to the at leastone objective lens 104 so that a first light source 106-1-A of the firstlight source set 106-1 opposes a first light source 106-2-A of thesecond light source set 106-2, a second light source 106-1-B of thefirst light source 106-1 set opposes a second light source 106-2-B ofthe second light source set 106-B, and a third light source 106-1-C ofthe first light source set 106-2 opposes a third light source 106-2-C ofthe second light source set 106-2-C with respect to the at least oneobjective lens 104. A first light (lights 106-1-A, 106-2-A) in eachlight source set in the plurality of light source sets is fired for afirst period of time while not firing the other light source in eachlight source set. A first set of images is collected during the firstperiod of time using at least a first subset of the plurality of pixelarray photo-sensors. A second light (light 106-1-B, 106-2-B) in eachlight source set in the plurality of light source sets is fired for asecond period of time while not firing the other light sources in eachlight source set. A second set of images is collected during the secondperiod of time using at least a second subset of the plurality of pixelarray photo-sensors. A third light (light 106-1-C, 106-2-C) in eachlight source set 106 in the plurality of light source sets is fired fora third period of time while not firing the other light sources in eachlight source set. A third set of images is collected during the thirdperiod of time using at least a third subset of the plurality of pixelarray photo-sensors. It will be appreciated that each set of lightsources may have any number of light sources (e.g., 2, 3, 4, 5, 6, 7, 8,or more).

Exemplary Optical Configurations

In one implementation, the imaging device 100 is configured to detect aset of spectral bands suitable for determining the oxyhemoglobin anddeoxyhemoglobin distribution in a tissue. In a specific implementation,this is achieved by capturing images of the tissue of interest at eightdifferent spectral bands. The images are captured in two exposures offour photo-sensors 210, each photo-sensor covered by a unique dual bandpass filter 216. In one implementation, the imaging device 100 has aplurality of light source sets and a first light source in eachrespective light source set is configured to concurrently illuminate thetissue of interest with light including exactly four of the eightspectral bands, where each dual band pass filter 216 has exactly onepass band matching a spectral band in the four spectral bands emittedfrom the first light source in each light source set. Each second lightin each respective light source set 106 is configured to concurrentlyilluminate the tissue of interest with light including the other fourspectral bands of the set of eight spectral bands (e.g., but not thefirst four spectral bands), where each dual band pass filter 216 hasexactly one pass band matching a spectral band in the four spectralbands emitted from second light source in each respective light sourceset.

In one implementation, the set of eight spectral bands includes spectralbands having central wavelengths of: 510±5 nm, 530±5 nm, 540±5 nm, 560±5nm, 580±5 nm, 590±5 nm, 620±5 nm, and 660±5 nm, and each spectral bandhas a full width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±4 nm, 530±4 nm, 540±4 nm, 560±4 nm,580±4 nm, 590±4 nm, 620±4 nm, and 660±4 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±3 nm, 530±3 nm, 540±3 nm, 560±3 nm,580±3 nm, 590±3 nm, 620±3 nm, and 660±3 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±2 nm, 530±2 nm, 540±2 nm, 560±2 nm,580±2 nm, 590±2 nm, 620±2 nm, and 660±2 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510±1 nm, 530±1 nm, 540±1 nm, 560±1 nm,580±1 nm, 590±1 nm, 620±1 nm, and 660±1 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 510 nm, 530 nm, 540 nm, 560 nm, 580 nm,590 nm, 620 nm, and 660 nm, and each spectral band has a full width athalf maximum of about 10 nm.

In one implementation, dual band filters having spectral pass bandscentered at: (i) 520±5 and 590±5, (ii) 540±5 and 610±5, (iii) 560±5 and620±5, and (iv) 580±5 and 640±5 are placed in front of photo-sensorsconfigured to detect this particular set of wavelengths.

In one implementation, the imaging device has a plurality of lightsource sets and a first light source in each such light source set isconfigured to illuminate a tissue of interest with light havingwavelengths from 450-585 nm in a first operation mode and a second lightsource in each respective light source set emits wavelengths from585-650 nm in a second operation mode. In one implementation, theimaging device has a plurality of light source sets and a first lightsource in each respective light source set is configured to illuminate atissue of interest with light having wavelengths from 450-585 nm, and asecond light source in each respective light source set is configured toilluminate the tissue of interest with light having wavelengths from585-650 nm.

In still another implementation, the imaging device has a plurality oflight source sets and a first light source in each respective lightsource set is configured to illuminate a tissue of interest with lighthaving wavelengths 520, 540, 560 and 640 but not wavelengths 580, 590,610 and 620 and a second light source in each respective light sourceset is configured to illuminate the tissue of interest with light havingwavelengths 580, 590, 610, and 620 but not wavelengths 520, 540, 560 and640.

In one implementation, dual band filters having spectral pass bandscentered at: (i) 520±5 and 560±5, (ii) 540±5 and 580±5, (iii) 590±5 and620±5, and (iv) 610 and 640±5 are placed in front of photo-sensorsconfigured to detect this particular set of wavelengths. In oneimplementation, the imaging device has a plurality of light source setsand a first light source in each such respective light source set isconfigured to illuminate a tissue of interest with light havingwavelengths from 450-550 nm and from 615-650 nm in a first operationmode and a second light source in each respective light source set emitswavelengths from 550-615 nm in a second operation mode.

In one implementation, the imaging device has a plurality of lightsource sets and a first light source in each respective light source isconfigured to illuminate a tissue of interest with light havingwavelengths from 450-550 nm and from 615-650 nm, and a second lightsource in each respective light source set is configured to illuminatethe tissue of interest with light having wavelengths from 585-650 nm.

In one implementation, dual band filters having spectral pass bandscentered at: (i) 520±5 and 560±5, (ii) 540±5 and 610±5, (iii) 590±5 and620±5, and (iv) 580 and 640±5 are placed in front of photo-sensorsconfigured to detect this particular set of wavelengths. In oneimplementation, the imaging device has a plurality of light source setsand a first light source in each light source set is configured toilluminate a tissue of interest with light having wavelengths from450-530 nm and from 600-650 nm in a first operation mode and secondlight source in each respective light source set is configured to emitswavelengths from 530-600 nm in a second operation mode. In oneimplementation, the imaging device has a plurality of light source setsand a first light source in each respective light source set isconfigured to illuminate a tissue of interest with light havingwavelengths from 450-530 nm and from 600-650 nm, and a second lightsource in each respective light source set is configured to illuminatethe tissue of interest with light having wavelengths from 530-600.

In one implementation, the set of eight spectral bands includes spectralbands having central wavelengths of: 520±5 nm, 540±5 nm, 560±5 nm, 580±5nm, 590±5 nm, 610±5 nm, 620±5 nm, and 640±5 nm, and each spectral bandhas a full width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±4 nm, 540±4 nm, 560±4 nm, 580±4 nm,590±4 nm, 610±4 nm, 620±4 nm, and 640±4 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±3 nm, 540±3 nm, 560±3 nm, 580±3 nm,590±3 nm, 610±3 nm, 620±3 nm, and 640±3 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±2 nm, 540±2 nm, 560±2 nm, 580±2 nm,590±2 nm, 610±2 nm, 620±2 nm, and 640±2 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520±1 nm, 540±1 nm, 560±1 nm, 580±1 nm,590±1 nm, 610±1 nm, 620±1 nm, and 640±1 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 520 nm, 540 nm, 560 nm, 580 nm, 590 nm,610 nm, 620 nm, and 640 nm, and each spectral band has a full width athalf maximum of about 10 nm.

In one implementation, the set of eight spectral bands includes spectralbands having central wavelengths of: 500±5 nm, 530±5 nm, 545±5 nm, 570±5nm, 585±5 nm, 600±5 nm, 615±5 nm, and 640±5 nm, and each spectral bandhas a full width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±4 nm, 530±4 nm, 545±4 nm, 570±4 nm,585±4 nm, 600±4 nm, 615±4 nm, and 640±4 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±3 nm, 530±3 nm, 545±3 nm, 570±3 nm,585±3 nm, 600±3 nm, 615±3 nm, and 640±3 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±2 nm, 530±2 nm, 545±2 nm, 570±2 nm,585±2 nm, 600±2 nm, 615±2 nm, and 640±2 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500±1 nm, 530±1 nm, 545±1 nm, 570±1 nm,585±1 nm, 600±1 nm, 615±1 nm, and 640±1 nm, and each spectral band has afull width at half maximum of less than 15 nm. In a relatedimplementation, the set of eight spectral bands includes spectral bandshaving central wavelengths of: 500 nm, 530 nm, 545 nm, 570 nm, 585 nm,600 nm, 615 nm, and 640 nm, and each spectral band has a full width athalf maximum of about 10 nm.

In other implementations, the imaging devices described here areconfigured for imaging more or less than eight spectral bands. Forexample, in some implementations, the imaging device is configured forimaging 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,21, 22, 23, 24, or more spectral bands. For example, imaging devicesincluding 7 beam splitters and eight photo-sensors can be configuredaccording to the principles described herein to capture eight imagesconcurrently, 16 images in two exposures (e.g., by placing dual bandpass filters in from of each photosensor), and 24 images in threeexposures (e.g., by placing triple band pass filters in front of eachphotosensor). In fact, the number of spectral band passes that can beimaged using the principles disclosed herein is only constrained by anydesired size of the imager, desired exposure times, and light sourcesemployed. Of course, one or more photo-sensors may not be used in anygiven exposure. For example, in an imaging device employing four photosensors and three beam splitters, seven images can be captured in twoexposures by not utilizing one of the photo-sensors in one of theexposures. Thus, imaging devices employing any combination of lightsources (e.g., 1, 2, 3, 4, or more), beam splitters (e.g., 1, 2, 3, 4,5, 6, 7, or more), and photo-sensors (e.g., 1, 2, 3, 4, 5, 6, 7, 8, ormore) are contemplated.

Optimization of Exposure Time

Many advantages of the imaging systems and methods described herein arederived, at least in part, from the use of in-band illumination anddetection across multiple spectral bands. For example, in-bandillumination allows for greater signal-to-noise ratio and reducedexposure times, which in turn results in lower power consumption,reduced misalignment due to movement of the subject, and reducedcomputational burden when processing the resulting hyperspectral datacubes.

These advantages can be further enhanced by minimizing the exposure time(e.g., shutter speed) needed to provide a suitable signal-to-noise ratioat each wavelength imaged. The minimum exposure time needed to resolve asuitable image at each wavelength will depend upon, at least, thesensitivity of the optical detector for the particular wavelength, thecharacteristics and intensity of ambient light present when acquiringimages, and the concentration of melanin in the skin/tissue beingimaged.

In one embodiment, the imaging systems described herein advantageouslyreduces the total amount of time required to collect a complete imageseries by determining the specific exposure time needed to resolve eachsub-image of the image series. Each image in the image series iscollected at a different spectral band and, because of this, the amountof time needed to resolve each sub-image will vary as a function ofwavelength. In some embodiments, this variance is advantageously takeninto account so that an image requiring less time, because of theiracquisition wavelengths or wavelength bands, are allotted shorterexposure times whereas images that require more time because of theiracquisition wavelengths or wavelength bands, are allotted shorterexposure times. This novel improvement affords a faster overall exposuretime because each of images in the series of images is only allocated anamount of time needed for full exposure, rather than a “one size fitsall” exposure time. This also reduces the power requirement of theimaging device, because the illumination, which requires a large amountof power, is shortened. In a specific embodiment, non-transitoryinstructions encoded by the imager in non-transient memory determine theminimal exposure time required for image acquisition at each spectralband acquired by the imaging system.

In some embodiments, the methods and systems described herein includeexecutable instructions for identifying a plurality of baseline exposuretimes, each respective baseline exposure time in the plurality ofbaseline exposure times representing an exposure time for resolving arespective image, in the series of images of the tissue being collected.A first baseline exposure time for a first image is different than asecond baseline exposure time of a second image in the plurality ofimages.

In one embodiment, a method is provided for acquiring an image series ofa tissue of a patient, including selecting a plurality of spectral bandsfor acquiring an image series of a tissue, identifying minimum exposuretimes for resolving an image of the tissue at each spectral band,identifying at least one factor affecting one of more minimum exposuretimes, adjusting the minimum exposure times based on the identifiedfactors, and acquiring a series of images of the tissue using theadjusted minimum exposure times.

In some embodiments, the minimum exposure times are based on baselineillumination of the tissue and/or the sensitivity of an optical detectoracquiring the image.

In some embodiments, the factor affecting the minimal exposure time isone or more of illumination provided by a device used to acquire theimage series, ambient light, and concentration of melanin in the tissue.

Hyperspectral Imaging

Hyperspectral and multispectral imaging are related techniques in largerclass of spectroscopy commonly referred to as spectral imaging orspectral analysis. Typically, hyperspectral imaging relates to theacquisition of a plurality of images, each image representing a narrowspectral band collected over a continuous spectral range, for example, 5or more (e.g., 5, 10, 15, 20, 25, 30, 40, 50, or more) spectral bandshaving a FWHM bandwidth of 1 nm or more each (e.g., 1 nm, 2 nm, 3 nm, 4nm, 5 nm, 10 nm, 20 nm or more), covering a contiguous spectral range(e.g., from 400 nm to 800 nm). In contrast, multispectral imagingrelates to the acquisition of a plurality of images, each imagerepresenting a narrow spectral band collected over a discontinuousspectral range.

For the purposes of the present disclosure, the terms “hyperspectral”and “multispectral” are used interchangeably and refer to a plurality ofimages, each image representing a narrow spectral band (having a FWHMbandwidth of between 10 nm and 30 nm, between 5 nm and 15 nm, between 5nm and 50 nm, less than 100 nm, between 1 and 100 nm, etc.), whethercollected over a continuous or discontinuous spectral range. Forexample, in various implementations, wavelengths 1-N of a hyperspectraldata cube 1336-1 are contiguous wavelengths or spectral bands covering acontiguous spectral range (e.g., from 400 nm to 800 nm). In otherimplementations, wavelengths 1-N of a hyperspectral data cube 1336-1 arenon-contiguous wavelengths or spectral bands covering a non-contiguousspectral ranges (e.g., from 400 nm to 440 nm, from 500 nm to 540 nm,from 600 nm to 680 nm, and from 900 to 950 nm).

As used herein, “narrow spectral range” refers to a continuous span ofwavelengths, typically consisting of a FWHM spectral band of no morethan about 100 nm. In certain embodiments, narrowband radiation consistsof a FWHM spectral band of no more than about 75 nm, 50 nm, 40 nm, 30nm, 25 nm, 20 nm, 15 nm, 10 nm, 5 nm, 4 nm, 3 nm, 2 nm, 1 nm, or less.In various implementations, wavelengths imaged by the methods anddevices disclosed herein are selected from one or more of the visible,near-infrared, short-wavelength infrared, mid-wavelength infrared,long-wavelength infrared, and ultraviolet (UV) spectrums.

By “broadband” it is meant light that includes component wavelengthsover a substantial portion of at least one band, for example, over atleast 20%, or at least 30%, or at least 40%, or at least 50%, or atleast 60%, or at least 70%, or at least 80%, or at least 90%, or atleast 95% of the band, or even the entire band, and optionally includescomponent wavelengths within one or more other bands. A “white lightsource” is considered to be broadband, because it extends over asubstantial portion of at least the visible band. In certainembodiments, broadband light includes component wavelengths across atleast 100 nm of the electromagnetic spectrum. In other embodiments,broadband light includes component wavelengths across at least 150 nm,200 nm, 250 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, or moreof the electromagnetic spectrum.

By “narrowband” it is meant light that includes components over only anarrow spectral region, for example, less than 20%, or less than 15%, orless than 10%, or less than 5%, or less than 2%, or less than 1%, orless than 0.5% of a single band. Narrowband light sources need not beconfined to a single band, but can include wavelengths in multiplebands. A plurality of narrowband light sources may each individuallygenerate light within only a small portion of a single band, buttogether may generate light that covers a substantial portion of one ormore bands, for example, may together constitute a broadband lightsource. In certain embodiments, broadband light includes componentwavelengths across no more than 100 nm of the electromagnetic spectrum(e.g., has a spectral bandwidth of no more than 100 nm). In otherembodiments, narrowband light has a spectral bandwidth of no more than90 nm, 80 nm, 75 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 25 nm, 20 nm, 15nm, 10 nm, 5 nm, or less of the electromagnetic spectrum.

As used herein, the “spectral bandwidth” of a light source refers to thespan of component wavelengths having an intensity that is at least halfof the maximum intensity, otherwise known as “full width at halfmaximum” (FWHM) spectral bandwidth. Many light emitting diodes (LEDs)emit radiation at more than a single discreet wavelength, and are thusnarrowband emitters. Accordingly, a narrowband light source can bedescribed as having a “characteristic wavelength” or “centerwavelength,” for example, the wavelength emitted with the greatestintensity, as well as a characteristic spectral bandwidth, for example,the span of wavelengths emitted with an intensity of at least half thatof the characteristic wavelength.

By “coherent light source” it is meant a light source that emitselectromagnetic radiation of a single wavelength in phase. Thus, acoherent light source is a type of narrowband light source with aspectral bandwidth of less than 1 nm. Non-limiting examples of coherentlight sources include lasers and laser-type LEDs. Similarly, anincoherent light source emits electromagnetic radiation having aspectral bandwidth of more than 1 nm and/or is not in phase. In thisregard, incoherent light can be either narrowband or broadband light,depending on the spectral bandwidth of the light.

Examples of suitable broadband light sources 106 include, withoutlimitation, incandescent lights such as a halogen lamp, xenon lamp, ahydrargyrum medium-arc iodide lamp, and a broadband light emitting diode(LED). In some embodiments, a standard or custom filter is used tobalance the light intensities at different wavelengths to raise thesignal level of certain wavelength or to select for a narrowband ofwavelengths. Broadband illumination of a subject is particularly usefulwhen capturing a color image of the subject or when focusing thehyperspectral/multispectral imaging system.

Examples of suitable narrowband, incoherent light sources 106 include,without limitation, a narrow band light emitting diode (LED), asuperluminescent diode (SLD) (see, Redding, B. et al, “Speckle-freelaser imaging”, arVix: 1110.6860 (2011), the content of which is herebyincorporated herein by reference in its entirety for all purposes), arandom laser, and a broadband light source covered by a narrow band-passfilter. Examples of suitable narrowband, coherent light sources 104include, without limitation, lasers and laser-type light emittingdiodes. While both coherent and incoherent narrowband light sources 104can be used in the imaging systems described herein, coherentillumination is less well suited for full-field imaging due to speckleartifacts that corrupt image formation (see, Oliver, B. M., “Sparklingspots and random diffraction”, Proc IEEE 51, 220-221 (1963)).

Hyperspectral Medical Imaging

Various implementations of the present disclosure provide for systemsand methods useful for hyperspectral/multispectral medical imaging(HSMI). HSMI relies upon distinguishing the interactions that occurbetween light at different wavelengths and components of the human body,especially components located in or just under the skin. For example, itis well known that deoxyhemoglobin absorbs a greater amount of light at700 nm than does water, while water absorbs a much greater amount oflight at 1200 nm, as compared to deoxyhemoglobin. By measuring theabsorbance of a two-component system consisting of deoxyhemoglobin andwater at 700 nm and 1200 nm, the individual contribution ofdeoxyhemoglobin and water to the absorption of the system, and thus theconcentrations of both components, can readily be determined. Byextension, the individual components of more complex systems (e.g.,human skin) can be determined by measuring the absorption of a pluralityof wavelengths of light reflected or backscattered off of the system.

The particular interactions between the various wavelengths of lightmeasured by hyperspectral/multispectral imaging and each individualcomponent of the system (e.g., skin) produceshyperspectral/multispectral signature, when the data is constructed intoa hyperspectral/multispectral data cube. Specifically, different regions(e.g., different regions of interest or ROI on a single subject ordifferent ROIs from different subjects) interact differently with lightdepending on the presence of, e.g., a medical condition in the region,the physiological structure of the region, and/or the presence of achemical in the region. For example, fat, skin, blood, and flesh allinteract with various wavelengths of light differently from one another.A given type of cancerous lesion interacts with various wavelengths oflight differently from normal skin, from non-cancerous lesions, and fromother types of cancerous lesions. Likewise, a given chemical that ispresent (e.g., in the blood, or on the skin) interacts with variouswavelengths of light differently from other types of chemicals. Thus,the light obtained from each illuminated region of a subject has aspectral signature based on the characteristics of the region, whichsignature contains medical information about that region.

The structure of skin, while complex, can be approximated as twoseparate and structurally different layers, namely the epidermis anddermis. These two layers have very different scattering and absorptionproperties due to differences of composition. The epidermis is the outerlayer of skin. It has specialized cells called melanocytes that producemelanin pigments. Light is primarily absorbed in the epidermis, whilescattering in the epidermis is considered negligible. For furtherdetails, see G. H. Findlay, “Blue Skin,” British Journal of Dermatology83(1), 127-134 (1970), the content of which is incorporated herein byreference in its entirety for all purposes.

The dermis has a dense collection of collagen fibers and blood vessels,and its optical properties are very different from that of theepidermis. Absorption of light of a bloodless dermis is negligible.However, blood-born pigments like oxy- and deoxyhemoglobin and water aremajor absorbers of light in the dermis. Scattering by the collagenfibers and absorption due to chromophores in the dermis determine thedepth of penetration of light through skin.

Light used to illuminate the surface of a subject will penetrate intothe skin. The extent to which the light penetrates will depend upon thewavelength of the particular radiation. For example, with respect tovisible light, the longer the wavelength, the farther the light willpenetrate into the skin. For example, only about 32% of 400 nm violetlight penetrates into the dermis of human skin, while greater than 85%of 700 nm red light penetrates into the dermis or beyond (see, CapineraJ. L., “Photodynamic Action in Pest Control and Medicine”, Encyclopediaof Entomology, 2nd Edition, Springer Science, 2008, pp. 2850-2862, thecontent of which is hereby incorporated herein by reference in itsentirety for all purposes). For purposes of the present disclosure, whenreferring to “illuminating a tissue,” “reflecting light off of thesurface,” and the like, it is meant that radiation of a suitablewavelength for detection is backscattered from a tissue of a subject,regardless of the distance into the subject the light travels. Forexample, certain wavelengths of infra-red radiation penetrate below thesurface of the skin, thus illuminating the tissue below the surface ofthe subject.

Briefly, light from the illuminator(s) on the systems described hereinpenetrates the subject's superficial tissue and photons scatter in thetissue, bouncing inside the tissue many times. Some photons are absorbedby oxygenated hemoglobin molecules at a known profile across thespectrum of light. Likewise for photons absorbed by de-oxygenatedhemoglobin molecules. The images resolved by the optical detectorsconsist of the photons of light that scatter back through the skin tothe lens subsystem. In this fashion, the images represent the light thatis not absorbed by the various chromophores in the tissue or lost toscattering within the tissue. In some embodiments, light from theilluminators that does not penetrate the surface of the tissue iseliminated by use of polarizers. Likewise, some photons bounce off thesurface of the skin into air, like sunlight reflecting off a lake.

Accordingly, different wavelengths of light may be used to examinedifferent depths of a subject's skin tissue. Generally, high frequency,short-wavelength visible light is useful for investigating elementspresent in the epidermis, while lower frequency, long-wavelength visiblelight is useful for investigating both the epidermis and dermis.Furthermore, certain infra-red wavelengths are useful for investigatingthe epidermis, dermis, and subcutaneous tissues.

In the visible and near-infrared (VNIR) spectral range and at lowintensity irradiance, and when thermal effects are negligible, majorlight-tissue interactions include reflection, refraction, scattering andabsorption. For normal collimated incident radiation, the regularreflection of the skin at the air-tissue interface is typically onlyaround 4%-7% in the 250-3000 nanometer (nm) wavelength range. Forfurther details, see Anderson, R. R. et al., “The Optics of Human Skin”,Journal of Investigative Dermatology, 77, pp. 13-19, 1981, the contentof which is hereby incorporated by reference in its entirety for allpurposes. When neglecting the air-tissue interface reflection andassuming total diffusion of incident light after the stratum corneumlayer, the steady state VNIR skin reflectance can be modeled as thelight that first survives the absorption of the epidermis, then reflectsback toward the epidermis layer due the isotropic scattering in thedermis layer, and then finally emerges out of the skin after goingthrough the epidermis layer again.

Accordingly, the systems and methods described herein can be used todiagnose and characterize a wide variety of medical conditions. In oneembodiment, the concentration of one or more skin or blood component isdetermined in order to evaluate a medical condition in a patient.Non-limiting examples of components useful for medical evaluationinclude: deoxyhemoglobin levels, oxyhemoglobin levels, total hemoglobinlevels, oxygen saturation, oxygen perfusion, hydration levels, totalhematocrit levels, melanin levels, collagen levels, and bilirubinlevels. Likewise, the pattern, gradient, or change over time of a skinor blood component can be used to provide information on the medicalcondition of the patient.

Non-limiting examples of conditions that can be evaluated byhyperspectral/multispectral imaging include: tissue ischemia, ulcerformation, ulcer progression, pressure ulcer formation, pressure ulcerprogression, diabetic foot ulcer formation, diabetic foot ulcerprogression, venous stasis, venous ulcer disease, peripheral arterydisease, atherosclerosis, infection, shock, cardiac decompensation,respiratory insufficiency, hypovolemia, the progression of diabetes,congestive heart failure, sepsis, dehydration, hemorrhage, hemorrhagicshock, hypertension, cancer (e.g., detection, diagnosis, or typing oftumors or skin lesions), retinal abnormalities (e.g., diabeticretinopathy, macular degeneration, or corneal dystrophy), skin wounds,burn wounds, exposure to a chemical or biological agent, and aninflammatory response.

In various embodiments, the systems and methods described herein areused to evaluate tissue oximetery and correspondingly, medicalconditions relating to patient health derived from oxygen measurementsin the superficial vasculature. In certain embodiments, the systems andmethods described herein allow for the measurement of oxygenatedhemoglobin, deoxygenated hemoglobin, oxygen saturation, and oxygenperfusion. Processing of these data provide information to assist aphysician with, for example, diagnosis, prognosis, assignment oftreatment, assignment of surgery, and the execution of surgery forconditions such as critical limb ischemia, diabetic foot ulcers,pressure ulcers, peripheral vascular disease, surgical tissue health,etc.

In various embodiments, the systems and methods described herein areused to evaluate diabetic and pressure ulcers. Development of a diabeticfoot ulcer is commonly a result of a break in the barrier between thedermis of the skin and the subcutaneous fat that cushions the footduring ambulation. This rupture can lead to increased pressure on thedermis, resulting in tissue ischemia and eventual death, and ultimatelymanifesting in the form of an ulcer (Frykberg R. G. et al., “Role ofneuropathy and high foot pressures in diabetic foot ulceration”,Diabetes Care, 21(10), 1998:1714-1719). Measurement of oxyhemoglobin,deoxyhemoglobin, and/or oxygen saturation levels byhyperspectral/multispectral imaging can provide medical informationregarding, for example: a likelihood of ulcer formation at an ROI,diagnosis of an ulcer, identification of boundaries for an ulcer,progression or regression of ulcer formation, a prognosis for healing ofan ulcer, the likelihood of amputation resulting from an ulcer. Furtherinformation on hyperspectral/multispectral methods for the detection andcharacterization of ulcers, e.g., diabetic foot ulcers, are found inU.S. Patent Application Publication No. 2007/0038042, and Nouvong, A. etal., “Evaluation of diabetic foot ulcer healing with hyperspectralimaging of oxyhemoglobin and deoxyhemoglobin”, Diabetes Care. 2009November; 32(11):2056-2061, the contents of which are herebyincorporated herein by reference in their entireties for all purposes.

Other examples of medical conditions include, but are not limited to:tissue viability (e.g., whether tissue is dead or living, and/or whetherit is predicted to remain living); tissue ischemia; malignant cells ortissues (e.g., delineating malignant from benign tumors, dysplasias,precancerous tissue, metastasis); tissue infection and/or inflammation;and/or the presence of pathogens (e.g., bacterial or viral counts).Various embodiments may include differentiating different types oftissue from each other, for example, differentiating bone from flesh,skin, and/or vasculature. Various embodiments may exclude thecharacterization of vasculature.

In various embodiments, the systems and methods provided herein can beused during surgery, for example to determine surgical margins, evaluatethe appropriateness of surgical margins before or after a resection,evaluate or monitor tissue viability in near-real time or real-time, orto assist in image-guided surgery. For more information on the use ofhyperspectral/multispectral imaging during surgery, see, Holzer M. S. etal., “Assessment of renal oxygenation during partial nephrectomy usinghyperspectral imaging”, J Urol. 2011 August; 186(2):400-4; Gibbs-StraussS. L. et al., “Nerve-highlighting fluorescent contrast agents forimage-guided surgery”, Mol Imaging. 2011 April; 10(2):91-101; andPanasyuk S. V. et al., “Medical hyperspectral imaging to facilitateresidual tumor identification during surgery”, Cancer Biol Ther. 2007March; 6(3):439-46, the contents of which are hereby incorporated hereinby reference in their entirety for all purposes.

For more information on the use of hyperspectral/multispectral imagingin medical assessments, see, for example: Chin J. A. et al., J VascSurg. 2011 December; 54(6):1679-88; Khaodhiar L. et al., Diabetes Care2007; 30:903-910; Zuzak K. J. et al., Anal Chem. 2002 May 1;74(9):2021-8; Uhr J. W. et al., Transl Res. 2012 May; 159(5):366-75;Chin M. S. et al., J Biomed Opt. 2012 February; 17(2):026010; Liu Z. etal., Sensors (Basel). 2012; 12(1):162-74; Zuzak K. J. et al., Anal Chem.2011 Oct. 1; 83(19):7424-30; Palmer G. M. et al., J Biomed Opt. 2010November-December; 15(6):066021; Jafari-Saraf and Gordon, Ann Vasc Surg.2010 August; 24(6):741-6; Akbari H. et al., IEEE Trans Biomed Eng. 2010August; 57(8):2011-7; Akbari H. et al., Conf Proc IEEE Eng Med Biol Soc.2009:1461-4; Akbari H. et al., Conf Proc IEEE Eng Med Biol Soc.2008:1238-41; Chang S. K. et al., Clin Cancer Res. 2008 Jul. 1;14(13):4146-53; Siddiqi A. M. et al., Cancer. 2008 Feb. 25;114(1):13-21; Liu Z. et al., Appl Opt. 2007 Dec. 1; 46(34):8328-34; ZhiL. et al., Comput Med Imaging Graph. 2007 December; 31(8):672-8;Khaodhiar L. et al., Diabetes Care. 2007 April; 30(4):903-10; Ferris D.G. et al., J Low Genit Tract Dis. 2001 April; 5(2):65-72; Greenman R. L.et al., Lancet. 2005 November 12; 366(9498):1711-7; Sorg B. S. et al., JBiomed Opt. 2005 July-August; 10(4):44004; Gillies R. et al., andDiabetes Technol Ther. 2003; 5(5):847-55, the contents of which arehereby incorporated herein by reference in their entirety for allpurposes.

It will also be understood that, although the terms “first,” “second,”etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another. For example, a first contact couldbe termed a second contact, and, similarly, a second contact could betermed a first contact, which changing the meaning of the description,so long as all occurrences of the “first contact” are renamedconsistently and all occurrences of the second contact are renamedconsistently. The first contact and the second contact are bothcontacts, but they are not the same contact.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the claims. Asused in the description of the embodiments and the appended claims, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willalso be understood that the term “and/or” as used herein refers to andencompasses any and all possible combinations of one or more of theassociated listed items. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

As used herein, the term “if” may be construed to mean “when” or “upon”or “in response to determining” or “in accordance with a determination”or “in response to detecting,” that a stated condition precedent istrue, depending on the context. Similarly, the phrase “if it isdetermined [that a stated condition precedent is true]” or “if [a statedcondition precedent is true]” or “when [a stated condition precedent istrue]” may be construed to mean “upon determining” or “in response todetermining” or “in accordance with a determination” or “upon detecting”or “in response to detecting” that the stated condition precedent istrue, depending on the context.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. An imaging device, comprising: A) a housinghaving an exterior and an interior; B) at least one objective lensattached to or within the housing, C) a plurality of light source setsradially disposed on the exterior of the housing about the at least oneobjective lens, wherein each light source set in the plurality of lightsource sets comprises a first light source that emits light that issubstantially limited to a first spectral range and a second lightsource that emits light that is substantially limited to a secondspectral range, each light source in each light source set in theplurality of light source sets is offset from the at least one objectivelens and positioned so that light from each respective light source isbackscattered by a tissue of a subject and then passed through the atleast one objective lens, and each light in each light source set has adifferent radial position with respect to the at least one objectivelens; D) a plurality of pixel array photo-sensors within the housing; E)an optical assembly within the interior of the housing, the opticalassembly in optical communication with the at least one objective lens,the optical assembly characterized by further directing light receivedby at least one objective lens from the tissue of the subject to atleast one pixel array photo-sensor in the plurality of pixel arrayphoto-sensors; F) a plurality of multi-bandpass filters, wherein eachrespective multi-bandpass filter in the plurality of multi-bandpassfilters covers a corresponding pixel array photo-sensor in the pluralityof pixel array photo-sensors thereby selectively allowing a differentcorresponding spectral band of light, from the light received by the atleast one object lens and redirected by the optical assembly, to passthrough to the corresponding pixel array photo-sensor; and G) acontroller, wherein at least one program is non-transiently stored inthe controller and executable by the controller, the at least oneprogram causing the controller to perform the method of: i) firing afirst light in each light source set in the plurality of light sourcesets for a first period of time while not firing the second light sourcein each light source set, ii) collecting a first set of images duringthe first period of time using at least a first subset of the pluralityof pixel array photo-sensors, iii) firing a second light in each lightsource set in the plurality of light source sets for a second period oftime while not firing the first light source in each light source set,and iv) collecting a second set of images during the second period oftime using at least a second subset of the plurality of pixel arrayphoto-sensors.
 2. The imaging device of claim 1, wherein the opticalassembly element comprises a plurality of beam splitters in opticalcommunication with the at least one objective lens and the plurality ofpixel array photo-sensors, each respective beam splitter in theplurality of beam splitters is configured to split the light received bythe at least one objective lens into at least two optical paths, a firstbeam splitter in the plurality of beam splitters is in direct opticalcommunication with the at least one objective lens and a second beamsplitter in the plurality of beam splitters is in indirect opticalcommunication with the at least one objective lens through the firstbeam splitter, and the plurality of beam splitters collectively splitlight received by the at least one objective lens into a plurality ofoptical paths, wherein each respective optical path in the plurality ofoptical paths is configured to direct light to a corresponding pixelarray photo-sensor in the plurality of pixel array photo-sensors throughthe respective multi-bandpass filter covering the corresponding pixelarray photo-sensor.
 3. The imaging device of claim 1, wherein theoptical assembly comprises a beam steering element characterized by aplurality of operating modes, each respective operating mode in theplurality of operating modes causing the beam steering element to be inoptical communication with a different pixel array photo-sensor in theplurality of pixel array photo-sensors, a first subset of the pluralityof operating modes are associated with firing a first light in eachlight source set in the plurality of light source sets in the firstperiod of time, and a second subset of the plurality of operating modesare associated with firing a second light in each light source set inthe plurality of light source sets in the second period of time.
 4. Theimaging device of claim 1, wherein the plurality of multi-bandpassfilters are dual bandpass filters.
 5. The imaging device of claim 1,wherein the plurality of light source sets consist of two light sourcesets, and a first light source set in the two light source sets isarranged with respect to the at least one objective lens so that thefirst light source of the first light source set opposes the first lightsource of the second light source set in the two light source sets, andthe second light source of the first light source set opposes the secondlight source of the second light source set.
 6. The imaging device ofclaim 1, wherein the plurality of light source sets consist of fourlight source sets, and a first light source set in the four light sourcesets is arranged with respect to the at least one objective lens so thatthe first light source of the first light source set opposes the firstlight source of a second light source set in the four light source sets,and the second light source of the first light source set opposes thesecond light source of the second light source set.
 7. The imagingdevice of claim 1, wherein the plurality of light source sets consist of2N light source sets, wherein N is a positive integer, and a first lightsource set in the 2N light source sets is arranged with respect to theat least one objective lens so that the first light source of the firstlight source set opposes the first light source of the second lightsource set in the 2N light source sets, and the second light source ofthe first light source set opposes the second light source of the secondlight source set.
 8. The imaging device of claim 1, wherein theplurality of light source sets collectively comprises a plurality offirst light sources and a plurality of second light sources, the firstplurality of first light sources are uniformly radially distributedabout the at least one objective lens, and the plurality of second lightsources are uniformly radially distributed about the at least oneobjective lens.
 9. The imaging device of claim 8, wherein the pluralityof first light sources are radially offset from the plurality of secondlight sources.
 10. The imaging device of claim 8, wherein the pluralityof light source sets consists of three light source sets.
 11. Theimaging device of claim 8, wherein the plurality of light source setscomprises four or more light source sets.
 12. The imaging device ofclaim 1, wherein the first light source of each light source set in theplurality of light source sets is a first multi-spectral light sourcecovered by a first bandpass filter, wherein the first bandpass filtersubstantially blocks all light emitted by the first light source otherthan the first spectral range, and the second light source of each lightsource set in the plurality of light source sets is a secondmulti-spectral light source covered by a second bandpass filter, whereinthe second bandpass filter substantially blocks all light emitted by thesecond light source other than the second spectral range.
 13. Theimaging device of claim 12, wherein the first multi-spectral lightsource is a first white light emitting diode and the secondmulti-spectral light source is a second white light emitting diode. 14.The imaging device of claim 1, wherein each respective multi-bandpassfilter in the plurality of multi-bandpass filters is configured toselectively allow light corresponding to either of two discrete spectralbands to pass through to the corresponding pixel array photo-sensor. 15.The imaging device of claim 14, wherein: a first of the two discretespectral bands corresponds to a first spectral band that is representedin the first spectral range and not in the second spectral range; and asecond of the two discrete spectral bands corresponds to a secondspectral band that is represented in the second spectral range and notin the first spectral range.
 16. The imaging device of claim 1, whereinthe first spectral range is substantially non-overlapping with thesecond spectral range.
 17. The imaging device of claim 1, wherein thefirst spectral range is substantially contiguous with the secondspectral range.
 18. The imaging device of claim 1, wherein the firstspectral range comprises 520 nm, 540 nm, 560 nm and 640 nm wavelengthlight and does not include 580 nm, 590 nm, 610 nm and 620 nm wavelengthlight, and the second spectral range comprises 580 nm, 590 nm, 610 nmand 620 nm wavelength light and does not include 520 nm, 540 nm, 560 nmand 640 nm wavelength light.
 19. The imaging device of claim 3, theoptical assembly further comprising a plurality of beam steeringelements, each respective beam steering element configured to directlight in a respective optical path to a respective pixel arrayphoto-sensor, of the plurality of pixel array photo-sensors,corresponding to the respective optical path.
 20. The imaging device ofclaim 19, wherein each one of a first subset of the plurality of beamsteering elements is configured to direct light in a first directionthat is perpendicular to the direction of the light received by theplurality of beam steering elements from the at least one objectivelens, and each one of a second subset of the plurality of beam steeringelements is configured to direct light in a second direction that isperpendicular to the light received by the plurality of beam steeringelements and opposite to the first direction.
 21. The imaging device ofclaim 1, wherein the first set of images includes, for each respectivepixel array photo-sensor in the plurality of pixel array photo-sensors,an image corresponding to a first spectral band transmitted by thecorresponding multi-bandpass filter, wherein the light falling withinthe first spectral range includes light falling within the firstspectral band of each multi-bandpass filter in the plurality ofmulti-bandpass filters, and wherein the second set of images includes,for each respective pixel array photo-sensor in the plurality of pixelarray photo-sensors, an image corresponding to a second spectral bandtransmitted by the corresponding multi-bandpass filter, wherein thelight falling within the second spectral range includes light fallingwithin the second spectral band of each multi-bandpass filter in theplurality of multi-bandpass filters.
 22. The imaging device of claim 21,wherein each respective pixel array photo-sensor in the plurality ofpixel array photo-sensors is a pixel array that is controlled by acorresponding shutter mechanism that determines an image integrationtime for the respective pixel array photo-sensor, and a first pixelarray photo-sensor in the plurality of pixel array photo-sensors isindependently associated with a first integration time for use duringthe collecting ii) and a second integration time for use during thecollecting iv), wherein the first integration time is independent of thesecond integration time.
 23. The imaging device of claim 2, wherein eachbeam splitter in the plurality of beam splitters exhibits a ratio oflight transmission to light reflection of about 50:50.
 24. The imagingdevice of claim 23, wherein each respective beam splitter in theplurality of beam splitters is a wavelength-independent beam splitters.25. The imaging device of claim 1, wherein each image in the pluralityof images is a multi-pixel image of the tissue of the subject, themethod further comprising: v) combining each image in the plurality ofimages, on a pixel by pixel basis, to form a composite image.
 26. Theimaging device of claim 1, wherein, the imaging device is portable andpowered independent of a power grid during first period of time and thesecond period of time, the plurality of light source sets collectivelycomprises a plurality of first light sources and a plurality of secondlight sources, the plurality of first light sources collectively provideat least 80 watts of illuminating power during the firing i), theplurality of second light sources collectively provide at least 80 wattsof illuminating power during the firing iii), and the imaging devicefurther comprises a capacitor bank in electrical communication with eachfirst light source and each second light source, wherein a capacitor inthe capacitor bank has a voltage rating of at least 2 volts and acapacitance rating of at least 80 farads.
 27. The imaging device ofclaim 1, wherein the two discrete bands of a multi-bandpass filter inthe plurality of multi-bandpass filters are separated by at least 60 nm.28. The imaging device of claim 1, wherein the imaging device isportable and electrically independent of a power grid during the firingi) and the firing iii), and wherein the firing i) occurs for less than300 milliseconds and the firing iii) occurs for less than 300milliseconds.
 29. The imaging device of claim 2, further comprising: afirst circuit board positioned on a first side of the optical assembly,wherein a first pixel array photo-sensor and a third pixel arrayphoto-sensor in the plurality of pixel array photo-sensors are coupledto the first circuit board; and a second circuit board positioned on asecond side of the optical assembly opposite to the first side, whereinthe second circuit board is substantially parallel with the firstcircuit board, wherein a second pixel array photo-sensor and a fourthpixel array photo-sensor in the plurality of pixel array photo-sensorsare coupled to the second circuit board, and wherein: the first beamsplitter is configured to split light received from the at least oneobjective lens into a first optical path and a second optical path,wherein the first optical path is substantially collinear with anoptical axis defined by the light incoming from at least one objectivelens to the optical assembly, and the second optical path issubstantially perpendicular to the optical axis, the second beamsplitter is configured split light from the first optical path into athird optical path and a fourth optical path, wherein the third opticalpath is substantially collinear with the first optical path, and thefourth optical path is substantially perpendicular to the optical axis,a third beam splitter in the plurality of beam splitters is configuredto split light from the second optical path into a fifth optical pathand a sixth optical path, wherein the fifth optical path issubstantially collinear with the second optical path, and the sixthoptical path is substantially perpendicular to the second optical path,and wherein the optical path assembly further comprises: a first beamsteering element configured to deflect light from the third optical pathperpendicular to the third optical path and onto the first pixel arrayphoto-sensor coupled to the first circuit board, a second beam steeringelement configured to deflect light from the fourth optical pathperpendicular to the fourth optical path and onto the second pixel arrayphoto-sensor coupled to the second circuit board, a third beam steeringelement configured to deflect light from the fifth optical pathperpendicular to the fifth optical path and onto the third pixel arrayphoto-sensor coupled to the first circuit board, and a fourth beamsteering element configured to deflect light from the sixth optical pathperpendicular to the sixth optical path and onto the fourth pixel arrayphoto-sensor coupled to the second circuit board.
 30. The imaging deviceof claim 29, wherein a first multi-bandpass filter in the plurality ofmulti-bandpass filters is positioned in the third optical path betweenthe first beam splitter and the first pixel array photo-sensor, a secondmulti-bandpass filter in the plurality of multi-bandpass filters ispositioned in the fourth optical path between the second beam splitterand the second pixel array photo-sensor, a third multi-bandpass filterin the plurality of multi-bandpass filters is positioned in the fifthoptical path between the third beam splitter and the third pixel arrayphoto-sensor, and a fourth multi-bandpass filter in the plurality ofmulti-bandpass filters is positioned in the sixth optical path betweenthe fourth beam splitter and the fourth pixel array photo-sensor. 31.The imaging device of claim 29, further comprising a polarizing filterdisposed along the optical axis.
 32. The imaging device of claim 29,wherein the polarizing filter is adjacent to the at least one objectivelens and before the first beam splitter along the optical axis.
 33. Theimaging device of claim 29, wherein the first beam steering element is afolding prism.
 34. The imaging device of claim 29, wherein eachrespective beam splitter and each respective beam steering element isoriented along substantially the same plane.
 35. The imaging device ofclaim 29, wherein the first beam splitter, the second beam splitter, andthe third beam splitter each exhibits a ratio of light transmission tolight reflection of about 50:50.
 36. The imaging device of claim 1,wherein the plurality of light source sets collectively comprises aplurality of first light sources and a plurality of second lightsources, each light source in the plurality of first light sources is awhite light-emitting diode covered by a respective first light sourcefilter that blocks light emitted by the white light-emitting diode otherthan the first spectral range, and each light source in the plurality ofsecond light sources is a white light-emitting diode covered by arespective second light source filter that blocks light emitted by thewhite light-emitting diode other than the second spectral range.
 37. Theimaging device of claim 1, wherein each light source in each lightsource set is covered by a first polarizer, and the at least oneobjective lens is covered by a second polarizer.
 38. The imaging deviceof claim 3, wherein the beam steering element comprises a mirror mountedon an actuator, the actuator having the plurality of operating modes.39. The imaging device of claim 38, wherein the mirror is asingle-surface mirror.
 40. The imaging device of claim 38, wherein themirror is a two-axis micro electro-mechanical (MEMS) mirror.
 41. Theimaging device of claim 3, wherein the beam steering element comprisesan array of micromirrors.
 42. The hyperspectral/multispectral imagingdevice of claim 41, wherein the array of micromirrors comprises adigital micromirror device.
 43. The imaging device of claim 3, whereinthe plurality of pixel array photo-sensors comprises at least four pixelarray photo-sensors.
 44. The imaging device of claim 1, wherein eachrespective pixel array photo-sensor in the plurality of pixel arrayphoto-sensors is used for detecting a different frequency of radiation.45. The imaging device of claim 3, wherein the collecting ii) comprisesplacing the beam steering element in an operating mode in the pluralityof operating modes that causes the beam steering element to be inoptical communication with a corresponding pixel array photo-sensor inthe plurality of pixel array photo-sensors.
 46. The imaging device ofclaim 1, further comprising a housing display disposed on the exteriorof the housing, the housing display in electronic communication with thecontroller, wherein the method further comprises displaying an imagecaptured by a respective pixel array photo-sensor in the plurality ofpixel array photo-sensors on the housing display.
 47. The imaging deviceof claim 1, wherein the plurality of light source sets comprises twolight source sets, and a first light source set in the two light sourcesets is arranged with respect to the at least one objective lens so thata first light source of the first light source set opposes a first lightsource of the second light source set, a second light source of thefirst light source set opposes a second light source of the second lightsource set, and a third light source of the first light source setopposes a third light source of the second light source set with respectto the at least one objective lens, and the method further comprises:iii) firing a third light in each light source set in the plurality oflight source sets for a third period of time while not firing the firstlight source or the second light source in each light source set, andiv) collecting a third set of images during the third period of timeusing at least a third subset of the plurality of pixel arrayphoto-sensors.
 48. The imaging device of claim 47, wherein a fourthlight source in the first light source set opposes a fourth light sourceof the second light source set in the two light source sets with respectto the at least one objective lens, and the method further comprises: v)firing a fourth light in each light source set in the plurality of lightsource sets for a fourth period of time while not firing the first lightsource, the second light source, or the third light source in each lightsource set, and vi) collecting a fourth set of images during the fourthperiod of time using at least a fourth subset of the plurality of pixelarray photo-sensors.
 49. The imaging device of claim 1 wherein eachlight source set in the plurality of light source sets consists of twolight sources.
 50. The imaging device of claim 1, wherein each lightsource set in the plurality of light source sets comprises 2+N lightsources, wherein N is a positive integer.